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The Direct Actions of Cannabidiol and 2-Arachidonoyl Glycerol at GABAA Receptors
Abstract
Cannabidiol (CBD) is a major non-intoxicating component of cannabis and possesses anti-epileptic, anxiolytic and anti-hyperalgesic properties. The mechanism of action of CBD in producing such effects remains unclear. Despite evidence that some endogenous and synthetic cannabinoids interact with GABAA receptors, no-one has yet investigated the effects of CBD. Here we used two-electrode voltage clamp electrophysiology to compare the actions of CBD with those of the major central endocannabinoid, 2-arachidonoyl glycerol (2-AG) on human recombinant GABAA receptors (synaptic α1-6βg2 and extrasynaptic α4β2δ) expressed on Xenopus oocytes. CBD and 2-AG were positive allosteric modulators at α1-6βγ2 receptors, with low micromolar potencies. The maximal level of enhancement seen with either CBD or 2-AG were on α2-containing GABAA receptor subtypes, with approximately a 4-fold enhancement of the GABA EC5 evoked current, more than twice the potentiation seen with other α-subunit receptor combinations. Further we observed β-subunit selectivity, whereby modulatory activity was higher at β2/β3 over β1 subunits. The β1-subunit homologous mutant β2(V436T) substantially diminished the efficacy of both drugs to a third of that obtained with wild-type β2 subunit combinations, but without changing potency. The potency of CBD increased and efficacy preserved in binary α1/α2β2 receptors indicating that their effects do not involve the classic benzodiazepine site. Exploration of extrasynaptic α4β2δ receptors revealed that both compounds enhanced GABA EC5 evoked currents at concentrations ranging from 0.01–1 μM. Taken together these results reveal a mode of action of CBD on specifically configured GABAA receptors that may be relevant to the anticonvulsant and anxiolytic effects of the compound.
... Several reports have shown modulation of Cys-loop receptors by phytocannabinoids and endocannabinoids independent of cannabinoid receptors with potential physiological or therapeutic consequences. It has been reported that exogenous and endogenous cannabinoids potentiate glycine receptors in a subunit-specific manner [15][16][17][18]; CBD and THC allosterically inhibit 5-HT 3 A macroscopic responses [19,20]; the endocannabinoid 2-arachidonoyl glycerol (2-AG), THC and CBD potentiate GABA A receptors [21,22]. With respect to α7 nAChR, it has been reported that anandamide, 2-AG, R-methanandamide, and CBD allosterically decrease macroscopic responses in oocytes and that CBD decreases choline-evoked currents in rat hippocampal slices [23][24][25]. ...
... THC neither decreases α7 nAChR channel frequency nor changes open and burst durations. However, THC is active at other Cys-loop receptors, including glycine, 5-HT 3 and GABA A receptors [16,18,[20][21][22]. CBD and THC share chemical structures, with the difference of the closure of a ring on THC as opposed to a free hydroxyl group in CBD. ...
... CBD modulation of Cys-loop receptors has pharmacological relevance. In this regard, CBD inhibition of 5-HT 3 receptors may contribute to its role in modulation of nociception and emesis, potentiation of GABA receptors may account for its anti-seizure, anxiolytic and analgesic effects, and potentiation of glycine receptors may be relevant for CBD anti-nociceptive actions [3,16,22]. Potentiation of α7 nAChR is required for improving cognition and memory and has neuroprotective, anti-nociceptive, and anti-inflammatory effects [14,33,34]. On the other hand, α7 nAChR mediates oncogenic signal transduction during cancer development, promotes cancer cell proliferation and metastasis in lung, gastrointestinal, and bladder tissues [35,68]. ...
Cannabidiol (CBD), an important terpenoid compound from marijuana with no psychoactive effects, has become of great pharmaceutical interest for several health conditions. As CBD is a multitarget drug, there is a need to establish the molecular mechanisms by which CBD may exert therapeutic as well as adverse effects. The α7 nicotinic acetylcholine receptor (α7 nAChR) is a cation-permeable ACh-gated channel present in the nervous system and in non-neuronal cells. It is involved in different pathological conditions, including neurological and neurodegenerative disorders, inflammation, and cancer. By high-resolution single-channel recordings and confocal microscopy, we here reveal how CBD modulates α7 nAChR ionotropic and metabotropic functions. CBD leads to a profound concentration-dependent decrease of α7 nAChR single-channel activity with an IC50 in the sub-micromolar range. The inhibition of α7 nAChR activity, which takes place through a membrane pathway, is neither mediated by receptor phosphorylation nor overcome by positive allosteric modulators and is compatible with CBD stabilization of resting or desensitized α7 nAChR conformational states. CBD modulation is complex as it also leads to the later appearance of atypical, low-frequency α7 nAChR channel openings. At the cellular level, CBD inhibits the increase in intracellular calcium triggered by α7 nAChR activation, thus decreasing cell calcium responses. The modulation of α7 nAChR is of pharmacological relevance and should be considered in the evaluation of CBD potential therapeutic uses. Thus, our study provides novel molecular information of CBD multiple actions and targets, which is required to set the basis for prospective applications in human health.
... In Xenopus oocytes expressing α1-6β2γ2 subunits of GABA A receptors, 2-AG potentiated currents activated low GABA concentrations (EC 5 = 0.1-10 µM) with EC 50 values ranging from 1.5 µM to 15.7 µM and significantly shifted GABA concentration-response curves to the left (Sigel et al., 2011; Frontiers in Physiology frontiersin.org Bakas et al., 2017). 2-AG also potentiated extrasynaptic δ-subunit containing α4β2δ GABA A receptors (Bakas et al., 2017). ...
... Bakas et al., 2017). 2-AG also potentiated extrasynaptic δ-subunit containing α4β2δ GABA A receptors (Bakas et al., 2017). Potentiation of GABA-evoked currents by 2-AG was significantly greater at GABA A -receptors containing a β2 or β3 subunit and markedly reduced by α2β2(V436T)γ2L and α2β2(VF439L)γ2L mutations in transmembrane domain 4 (Sigel et al., 2011). ...
... CBD has been shown to act as a positive allosteric modulator, with EC 50 values ranging from 0.9 µM to 16.1 µM and magnitudes of potentiation in the range of 72%-332% at αβγ2 receptor combinations, with higher level of potentiation on α2 containing subtype combination (Bakas et al., 2017). The greatest levels of enhancements by CBD were reported as 332% on α2β2γ2L and 752% on α4β2δ subunit combinations and the classical benzodiazepine binding site located at α-γ2L interface does not seem to be involved in CBD interaction with GABA A receptors. ...
Phytocannabinoids such as Δ ⁹ -tetrahydrocannabinol and cannabidiol, endocannabinoids such as N-arachidonoylethanolamine (anandamide) and 2-arachidonoylglycerol, and synthetic cannabinoids such as CP47,497 and JWH-018 constitute major groups of structurally diverse cannabinoids. Along with these cannabinoids, CB1 and CB2 cannabinoid receptors and enzymes involved in synthesis and degradation of endocannabinoids comprise the major components of the cannabinoid system. Although, cannabinoid receptors are known to be involved in anti-convulsant, anti-nociceptive, anti-psychotic, anti-emetic, and anti-oxidant effects of cannabinoids, in recent years, an increasing number of studies suggest that, at pharmacologically relevant concentrations, these compounds interact with several molecular targets including G-protein coupled receptors, ion channels, and enzymes in a cannabinoid-receptor independent manner. In this report, the direct actions of endo-, phyto-, and synthetic cannabinoids on the functional properties of ligand-gated ion channels and the plausible mechanisms mediating these effects were reviewed and discussed.
... Phospholipase C and diacylglycerol lipase (DAGL) are two enzymes involved in synthesizing 2-arachidonoylglycerol (2-AG) [151]. Additionally, it has been revealed that cannabidiol acts as a positive allosteric modulator at GABAA receptors, and observational trials have shown that CBD in the formulation of Epidiolex is indeed an effective analgesic in the treatment of Lennox-Gastaut disorder and Dravet syndrome [152,153]. By controlling the balance of interneurons transmission, CBD's potential to increase endogenous cannabinoid production levels and promote the GABAergic transfer of information may aid in restoring neuronal function and neuroplasticity [152,153]. ...
... Additionally, it has been revealed that cannabidiol acts as a positive allosteric modulator at GABAA receptors, and observational trials have shown that CBD in the formulation of Epidiolex is indeed an effective analgesic in the treatment of Lennox-Gastaut disorder and Dravet syndrome [152,153]. By controlling the balance of interneurons transmission, CBD's potential to increase endogenous cannabinoid production levels and promote the GABAergic transfer of information may aid in restoring neuronal function and neuroplasticity [152,153]. In ASD and Fragile X Syndrome (FXS), in which patients do not have seizures, CBD treatment has been proven to help in both animal and human models. ...
Autism spectrum disorder (ASD) is a developmental disorder that causes difficulty while socializing and communicating and the performance of stereotyped behavior. ASD is thought to
have a variety of causes when accompanied by genetic disorders and environmental variables together, resulting in abnormalities in the brain. A steep rise in ASD has been seen regardless of the
numerous behavioral and pharmaceutical therapeutic techniques. Therefore, using complementary and alternative therapies to treat autism could be very significant. Thus, this review is completely
focused on non-pharmacological therapeutic interventions which include different diets, supplements, antioxidants, hormones, vitamins and minerals to manage ASD. Additionally, we also focus
on complementary and alternative medicine (CAM) therapies, herbal remedies, camel milk and cannabiodiol. Additionally, we concentrate on how palatable phytonutrients provide a fresh glimmer of hope in this situation. Moreover, in addition to phytochemicals/nutraceuticals, it also focuses on various microbiomes, i.e., gut, oral, and vaginal. Therefore, the current comprehensive review opens a new avenue for managing autistic patients through non-pharmacological intervention.
... Considering that ABHD6 both hydrolyzes 2-AG and is expressed in postsynaptic terminals, 2-AG represents the most likely candidate that links ABHD6 inhibition to potentiation of GABA A R currents. Specifically, 2-AG binds to an intracellular allosteric binding site on GABA A R, suggesting that localized subcellular increases in post-synaptic 2-AG due to ABHD6 inhibition are likely sufficient to potentiate tonic GABA A R currents (Bakas et al., 2017;Sigel et al., 2011). ...
... These results suggest that absence of ABHD6 expression might accelerate Scn1a +/− -mediated disease progression through a different mechanism than control of seizures. ABHD6 is a multifunctional protein that contains serine-dependent catalytic domain involved in 2-AG hydrolysis and a protein-interacting domain involved in the trafficking of AMPA receptor subunits to the plasma membrane (Bakas et al., 2017). Accordingly, genetic deletion of ABHD6 expression will likely impair AMPA receptors during early development, which is likely to enhance the detrimental effect of Scn1a +/− on early development. ...
Evidence suggests that inhibition of α/β hydrolase-domain containing 6 (ABHD6) reduces seizures; however, the molecular mechanism of this therapeutic response remains unknown. We discovered that heterozygous expression of Abhd6 (Abhd6+/−) significantly reduced the premature lethality of Scn1a+/− mouse pups, a genetic mouse model of Dravet Syndrome (DS). Both Abhd6+/− mutation and pharmacological inhibition of ABHD6 reduced the duration and incidence of thermally induced seizures in Scn1a+/− pups. Mechanistically, the in vivo anti-seizure response resulting from ABHD6 inhibition is mediated by potentiation of gamma-aminobutyric acid receptors Type-A (GABAAR). Brain slice electrophysiology showed that blocking ABHD6 potentiates extrasynaptic (tonic) GABAAR currents that reduce dentate granule cell excitatory output without affecting synaptic (phasic) GABAAR currents. Our results unravel an unexpected mechanistic link between ABHD6 activity and extrasynaptic GABAAR currents that controls hippocampal hyperexcitability in a genetic mouse model of DS.
Brief summary
This study provides the first evidence for a mechanistic link between ABHD6 activity and the control of extrasynaptic GABAAR currents that controls hippocampal hyperexcitability in a genetic mouse model of Dravet Syndrome and can be targeted to dampened seizures.
... GABA Receptors GABA (main inhibitory neurotransmitter) binds to GABA A receptors promoting a rapid influx of chloride ions and resulting in hyperpolarization and inhibition of the cell [68,69]. Interestingly, GABA A receptors represent a target for CBD, either enhancing inhibitory GABA A receptor activation [70], potentiating GABA-mediated inhibitory currents [71], or enhancing the amplitude of the GABA-evoked currents [72]. ...
... Additionally, abnormalities of GABAergic transmission have been associated with epilepsy development [110,111]. CBD has been reported as a positive allosteric modulator of GABA A receptors [71,112], possibly enhancing GABAergic inhibitory transmission and explaining additional CBD's anti-seizure effects. ...
The use of Cannabis for medicinal purposes has been documented since ancient times, where one of its principal cannabinoids extracted from Cannabis sativa, cannabidiol (CBD), has emerged over the last few years as a promising molecule with anti-seizure potential. Here, we present an overview of recent literature pointing out CBD’s pharmacological profile (solubility, metabolism, drug-drug interactions, etc.,), CBD’s interactions with multiple molecular targets as well as advances in preclinical research concerning its anti-seizure effect on both acute seizure models and chronic models of epilepsy. We also highlight the recent attention that has been given to other natural cannabinoids and to synthetic derivatives of CBD as possible compounds with therapeutic anti-seizure potential. All the scientific research reviewed here encourages to continue to investigate the probable therapeutic efficacy of CBD and its related compounds not only in epilepsy but also and specially in drug-resistant epilepsy, since there is a dire need for new and effective drugs to treat this disease.
... These subunit changes can modify GABA A R's function, often determining a reduced inhibitory tone and altering the effectiveness of ASMs on the original molecular target [51]. This hypothesis is strengthened by several studies that clearly showed CBD's ability to modulate different GABA A R subunit compositions [17,45], such as α2, α3 and α6, indicating, thus, that its action is not linked to the different α subunit expressions. In the aforementioned conditions, drugs targeting new and alternative modulatory sites on GABA A Rs are likely to yield better results compared to classical ASMs. ...
... This last finding suggests that CBD may act also on defective GABA A Rs, especially in those conditions where BDZs are partially or completely ineffective [52]. Interestingly, as demonstrated in other studies [17], CBD is also able to modulate δ-containing GABA A Rs, making it an interesting pharmacological tool to potentially treat other epileptic pharmaco-resistant conditions characterized by a dysfunction of "tonic" GABA A R neurotransmission [53]. Further studies are required in order to better characterize CBD's modulation of GABA A R's function and identify the exact site of CBD binding on human GABA A Rs. ...
Recently, the potential use of phytocannabinoids (pCBs) to treat different pathological conditions has attracted great attention in the scientific community. Among the different pCBs, cannabidiol (CBD) has showed interesting biological properties, making it a promising molecule with a high security profile that has been approved for treatment as an add-on therapy in patients afflicted by severe pharmaco-resistant epilepsy, including Dravet syndrome (DS), Lennox–Gastaut syndrome (LGS) and tuberous sclerosis complex (TSC). CBD is pharmacologically considered a “dirty drug”, since it has the capacity to bind different targets and to activate several cellular pathways. GABAergic impairment is one of the key processes during the epileptogenesis period able to induce a generalized hyperexcitability of the central nervous system (CNS), leading to epileptic seizures. Here, by using the microtransplantation of human brain membranes approach in Xenopus oocytes and electrophysiological recordings, we confirm the ability of CBD to modulate GABAergic neurotransmission in human cerebral tissues obtained from patients afflicted by different forms of pharmaco-resistant epilepsies, such as DS, TSC, focal cortical dysplasia (FCD) type IIb and temporal lobe epilepsy (TLE). Furthermore, using cDNAs encoding for human GABAA receptor subunits, we found that α1β2 receptors are still affected by CBD, while classical benzodiazepine lost its efficacy as expected.
... CBD is known to interact with multiple neurotransmitter systems within the brain. In addition to CB1 and CB2 cannabinoid receptors, it also has actions at 5-HT 1A receptors, TRPV1 receptor, and GABAergic systems (Bakas et al., 2017;Cifelli et al., 2020;Kaplan et al., 2017;Osborne et al., 2019;Pretzsch et al., 2019;Vitale et al., 2021). Of particular relevance to the present study is the finding that CBD acts as a positive allosteric modulator at extrasynaptic GABA A receptors with the α4βδ subunit configuration (Bakas et al., 2017). ...
... In addition to CB1 and CB2 cannabinoid receptors, it also has actions at 5-HT 1A receptors, TRPV1 receptor, and GABAergic systems (Bakas et al., 2017;Cifelli et al., 2020;Kaplan et al., 2017;Osborne et al., 2019;Pretzsch et al., 2019;Vitale et al., 2021). Of particular relevance to the present study is the finding that CBD acts as a positive allosteric modulator at extrasynaptic GABA A receptors with the α4βδ subunit configuration (Bakas et al., 2017). Interestingly, the neuroactive metabolite of progesterone allopregnanolone (ALLO) has a similar action (Paul and Purdy, 1992). ...
Rationale:
Cannabidiol (CBD), the major non-psychoactive constituent of cannabis, has therapeutic potential for the treatment of anxiety. Most preclinical studies investigate only acute effects of CBD and only in males, yet the drug is most likely to be used over a sustained period in clinical practice.
Objectives:
The objectives of this study were to investigate the anxiolytic-like effect of CBD in female rats compared to males and to determine whether the responsiveness of females was influenced by the stage of the estrous cycle.
Methods:
We carried out experiments to compare the effect of CBD in male and female rats in the elevated plus maze (EPM) in response to acute and short-term (4 days) administration through a complete cycle in females.
Results:
Male and female rats behaved in a similar manner in the EPM, but females in the late diestrus (LD) phase exhibited more anxiety-like behavior than at other stages, the difference reaching statistical significance compared to proestrus stages. CBD produced anxiolytic-like effects in both sexes, but female rats were responsive only in LD and 10-fold lower dose than males. After sub-chronic (4 days) treatment, responsiveness to CBD was maintained in females in LD, but females in proestrus remained unresponsive to CBD treatment.
Conclusions:
We suggest that there are sex differences in the anxiolytic-like effects of CBD in rats that reflect different underlying mechanisms: based on literature data, gonadal hormone status linked to GABAA receptor expression in females, and 5-HT1A receptor activation in males.
... The rapid decline in secretion of progesterone, and consequent decrease of its neuroactive metabolite allopregnanolone triggers upregulation of extrasynaptic GABA A receptors with the α4βδ subunit configuration in panic circuitry and a subsequent increase in neuronal excitability [46,47]. In an in vitro model using Xenopus oocytes expressing synaptic human recombinant GABA receptors (α16βγ2 and extrasynaptic α4β2δ) CBD behaved as a positive allosteric modulator at GABA A receptors with the α4βδ subunit configuration [74]. Therefore, it is possible to speculate that acute CBD administration in late diestrus may substitute for the actions of ALLO as its concentration declines, thereby preventing the "withdrawal" effect that precipitates the disturbance in GABA signalling and increased anxiety-like behaviour that usually characterises this cycle phase [21]. ...
... It was suggested that the action of CBD on specifically configured GABAA receptors does not involve the classical benzodiazepine site and may have relevance to the anticonvulsant and anxiolytic effects of the compound. In addition, it was suggested that CBD could restore physiological GABAergic transmission (Bakas et al. 2017;Cifelli et al. 2020;Olafuyi et al. 2022). ...
Despite the fact that there are several drugs available for the treatment of epilepsy, pharmacoresistance remains a major challenge in seizure control. Therefore, a significant part of epilepsy research has focused on revealing the mechanisms underlying drug resistance in order to develop new rationally designed pharmaceutical therapies for refractory epilepsies. Based on experimental and clinical studies, epilepsy-induced structural and functional alterations in brain targets have been postulated to lead to decreased sensitivity to antiepileptic drugs, more recently antiseizure medications (ASM). Also, evidence shows that GABA neurotransmission system plays a leading role in the pathophysiology of epilepsy. Canonically, GABA (gamma-aminobutyric acid) is considered the main inhibitory neurotransmitter in the central nervous system, but due to the variability in the location and composition of its receptors by different types of subunits, as well as neural physiological immaturity, GABA may have excitatory effects. Abnormalities in the GABAergic system identified in animal models of epilepsy and in samples of brain tissue samples resected surgically from patients with drug-resistant epilepsy, mainly at level of GABAA receptors (GABAARs), whose changes lead to an altered response to some ASMs, among other neuroleptic drugs.Here we review the current evidence on changes in the GABAergic system related to seizure generation, epilepsy, and pharmacoresistance, with particular emphasis on GABAARs and genetic polymorphisms of its subunits associated with refractory human epilepsy.KeywordsPharmacoresistant epilepsyGABA neurotransmissionGABAReceptorsHuman dataAnimal modelsGABA geneticsAntiseizure medication
... Gamma-aminobutyric acid (GABA) plays a key role in vertebrates' central nervous systems, facilitating a rapid inhibitory neurotransmission, and causing brain hyperexcitability through its interactions with GABAA receptors. CBD is an allosteric modulator of GABAA receptors, and amplifies the currents produced by low, but not by high, GABA concentrations, effectively increasing GABA's apparent affinity for its receptor [49]. ...
Cannabidiol (CBD) is the primary non-psychoactive chemical from Cannabis Sativa, a plant used for centuries for both recreational and medicinal purposes. CBD lacks the psychotropic effects of Δ9-tetrahydrocannabinol (Δ9-THC) and has shown great therapeutic potential. CBD exerts a wide spectrum of effects at a molecular, cellular, and organ level, affecting inflammation, oxidative damage, cell survival, pain, vasodilation, and excitability, among others, modifying many physiological and pathophysiological processes. There is evidence that CBD may be effective in treating several human disorders, like anxiety, chronic pain, psychiatric pathologies, cardiovascular diseases, and even cancer. Multiple cellular and pre-clinical studies using animal models of disease and several human trials have shown that CBD has an overall safe profile. In this review article, we summarize the pharmacokinetics data, the putative mechanisms of action of CBD, and the physiological effects reported in pre-clinical studies to give a comprehensive list of the findings and major effects attributed to this compound.
... In earlier studies, CBD, in the concentration range of 1-30 μM, has been shown to modulate the functions of ligandgated ion channels including nicotinic α 7 (Mahgoub et al., 2013), 5-HT 3 (Yang et al., 2010), glycine (Ahrens et al., 2009), and GABA A (Bakas et al., 2017) receptors as well as voltage-gated Na + (Ghovanloo et al., 2018), L-type Ca 2+ (Ali et al., 2015), T-type Ca 2+ (Ross et al., 2008) and K + (Orvos et al., 2020) channels. Drugs interacting with such a large repertoire of ion channels can legitimately be suspected to cause cardiac safety concerns due to their arrhythmogenic potential. ...
... Further ionotropic receptors negatively modulated by CBD are TRPM8, which is directly antagonized [78], and the α7 nicotinic acetylcholine receptor and the serotonin receptor 5HT3a [79,80] on which CBD acts as a negative allosteric modulator. A positive allosteric modulator of CBD has been observed for anionic ion channels, such as glycine (GlyRs) and GABA A receptors [81,82]. CBD also acts on voltage-gated calcium Cav3.1/Cav3.2 and sodium channels Cav3.3, inhibiting cationic currents, as well as decreasing the conductance of voltage-dependent anion channel 1 (VDAC1) [83][84][85]. ...
The medical use of cannabis has a very long history. Although many substances called cannabinoids are present in cannabis, Δ9tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD) and cannabinol (CBN) are the three main cannabinoids that are most present and described. CBD itself is not responsible for the psychotropic effects of cannabis, since it does not produce the typical behavioral effects associated with the consumption of this drug. CBD has recently gained growing attention in modern society and seems to be increasingly explored in dentistry. Several subjective findings suggest some therapeutic effects of CBD that are strongly supported by research evidence. However, there is a plethora of data regarding CBD’s mechanism of action and therapeutic potential, which are in many cases contradictory. We will first provide an overview of the scientific evidence on the molecular mechanism of CBD’s action. Furthermore, we will map the recent developments regarding the possible oral benefits of CBD. In summary, we will highlight CBD’s promising biological features for its application in dentistry, despite exiting patents that suggest the current compositions for oral care as the main interest of the industry.
... Further ionotropic receptors negatively modulated by CBD are TRPM8, which is directly antagonized [78], and α7 nicotinic acetylcholine receptor and serotonin receptor 5HT3a [79,80] on which CBD acts as a negative allosteric modulator. Positive allosteric modulator by CBD has been observed for anionic ion channels, such as glycine (GlyRs) and GABAA receptors [81,82]. CBD also acts on voltage-gated calcium Cav3.1/Cav3.2 and sodium channels Cav3.3, inhibiting cationic currents, as well as decreasing the conductance of voltagedependent anion channel 1 (VDAC1) [83][84][85]. ...
The medical use of Cannabis has a very long history. Although many principles are present in cannabis, called cannabinoids, Δ9tetrahydrocannabinol (Δ9-THC), cannabidiol (CBD) and can-nabinol (CBN) are the three main cannabinoids most present and described. CBD itself is not re-sponsible for psychotropic effects of cannabis since does not produce the typical behavioral effects associated to the consumption of this drug. Cannabidiol (CBD) has recently gained growing at-tention in modern society and seems to be more and more explored in dentistry. Several subjective findings suggest some therapeutic effects of CBD, which are strongly supported by research evi-dence. However, there is a plethora of data regarding CBD’s mechanism of action and therapeutic potential, which are in many cases contradictory. We will first provide an overview of scientific evidence on the molecular mechanism of CBD’s action. Furthermore, we will map the recent de-velopments regarding possible oral benefits of CBD. In summary, we will highlight CBD’s prom-ising biological features for dentistry application, despite exiting patents suggest current the compositions for oral care as the main interest for industry.
... CBD acts as an inverse agonist of the G-protein-coupled orphan receptors, GPR3, GPR6, and GPR12, which are involved in Parkinson's, Huntington's, and multiple sclerosis (Peres et al. 2018). Moreover, CBD was shown to act as a positive allosteric modulator at all α-containing GABA A Rs (Bakas et al. 2017). More recently, CBD was shown to act as an orexin 1 receptor antagonist (Vitale et al. 2021). ...
Among individuals with alcohol use disorder (AUD), it is estimated that the majority suffer from persistent sleep disturbances for which few candidate medications are available. Our aim wass to critically review the potential for cannabidiol (CBD) as a treatment for AUD-induced sleep disturbance. As context, notable side effects and abuse liability for existing medications for AUD-induced sleep disturbance reduce their clinical utility. CBD modulation of the endocannabinoid system and favorable safety profile have generated substantial interest in its potential therapeutic use for various medical conditions. A number of preclinical and clinical studies suggest promise for CBD in restoring the normal sleep-wake cycle and in enhancing sleep quality in patients diagnosed with AUD. Based on its pharmacology and the existing literature, albeit primarily preclinical and indirect, CBD is a credible candidate to address alcohol-induced sleep disturbance. Well-designed RCTs will be necessary to test its potential in managing this challenging feature of AUD.
... We hypothesize that metformin could have an effect also on IN development and maturation due to its effect on MMP-9 expression. In addition, cannabidiol has a positive allosteric modulation on GABA A receptors (Bakas et al., 2017), enhancing GABAergic transmission, and improves the balance in inhibitory and excitatory transmission, restoring neuronal function and synaptic plasticity in patients with FXS (Palumbo et al., 2023). ...
Fragile X Syndrome (FXS) is the most common form of inherited intellectual disability (ID) and a primary genetic cause of autism spectrum disorder (ASD). FXS arises from the silencing of the FMR1 gene causing the lack of translation of its encoded protein, the Fragile X Messenger RibonucleoProtein (FMRP), an RNA-binding protein involved in translational control and in RNA transport along dendrites. Although a large effort during the last 20 years has been made to investigate the cellular roles of FMRP, no effective and specific therapeutic intervention is available to treat FXS. Many studies revealed a role for FMRP in shaping sensory circuits during developmental critical periods to affect proper neurodevelopment. Dendritic spine stability, branching and density abnormalities are part of the developmental delay observed in various FXS brain areas. In particular, cortical neuronal networks in FXS are hyper-responsive and hyperexcitable, making these circuits highly synchronous. Overall, these data suggest that the excitatory/inhibitory (E/I) balance in FXS neuronal circuitry is altered. However, not much is known about how interneuron populations contribute to the unbalanced E/I ratio in FXS even if their abnormal functioning has an impact on the behavioral deficits of patients and animal models affected by neurodevelopmental disorders. We revise here the key literature concerning the role of interneurons in FXS not only with the purpose to better understand the pathophysiology of this disorder, but also to explore new possible therapeutic applications to treat FXS and other forms of ASD or ID. Indeed, for instance, the re-introduction of functional interneurons in the diseased brains has been proposed as a promising therapeutic approach for neurological and psychiatric disorders.
... It has been described that in GABA-A R transfected into Xenopus laevis oocytes, CBD is capable of increasing GABA-A R mediated currents in a dose-dependent manner, with the β subunit being the main binding site for it. Therefore, CBD is a PAM of GABA-A R in micromolar concentration ranges [58]. This mechanism of action seems to be related with the anxiolytic and anticonvulsant effects exerted by CBD [41]. ...
Cannabidiol (CBD) is a major phytocannabinoid present in Cannabis sativa (Linneo, 1753). This naturally occurring secondary metabolite does not induce intoxication or exhibit the characteristic profile of drugs of abuse from cannabis like Δ9-tetrahydrocannabinol (∆9-THC) does. In contrast to ∆9-THC, our knowledge of the neuro-molecular mechanisms of CBD is limited, and its pharmacology, which appears to be complex, has not yet been fully elucidated. The study of the pharmacological effects of CBD has grown exponentially in recent years, making it necessary to generate frequently updated reports on this important metabolite. In this article, a rationalized integration of the mechanisms of action of CBD on molecular targets and pharmacological implications in animal models and human diseases, such as epilepsy, pain, neuropsychiatric disorders, Alzheimer’s disease, and inflammatory diseases, are presented. We identify around 56 different molecular targets for CBD, including enzymes and ion channels/metabotropic receptors involved in neurologic conditions. Herein, we compiled the knowledge found in the scientific literature on the multiple mechanisms of actions of CBD. The in vitro and in vivo findings are essential for fully understanding the polypharmacological nature of this natural product.
... In this sense, mental states characterized by stress induce ROS by altering the balance of excitatory neurotransmitters (adrenaline, glutamate), serotonin, and GABA, which also modulate the immune response and maintain the body's homeostasis and the functionality of the hypothalamic-pituitary-adrenal axis (HPA) [166]. For this purpose, in post-traumatic stress syndrome (PTSD), CBD finds applicability by blocking FAAH and increasing available AEA [167][168][169]; in depression, CBD alleviates symptoms by stimulating serotoninergic neurotransmission, mediated by 5-HT 1A , and by activating the BDNF-TrkB complex [170][171][172], whereas in anxiety and fear, these beneficial effects are mediated by the same 5-HT 1A receptor, but also by GABA A receptors, respectively, by inhibiting the enzymatic activity of iNOS and FAAH [173]. ...
The literature provides scientific evidence for the beneficial effects of cannabidiol (CBD), and these effects extend beyond epilepsy treatment (e.g., Lennox–Gastaut and Dravet syndromes), notably the influence on oxidative status, neurodegeneration, cellular protection, cognitive function, and physical performance. However, products containing CBD are not allowed to be marketed everywhere in the world, which may ultimately have a negative effect on health as a result of the uncontrolled CBD market. After the isolation of CBD follows the discovery of CB1 and CB2 receptors and the main enzymatic components (diacylglycerol lipase (DAG lipase), monoacyl glycerol lipase (MAGL), fatty acid amino hydrolase (FAAH)). At the same time, the antioxidant potential of CBD is due not only to the molecular structure but also to the fact that this compound increases the expression of the main endogenous antioxidant systems, superoxide dismutase (SOD), and glutathione peroxidase (GPx), through the nuclear complex erythroid 2-related factor (Nrf2)/Keep1. Regarding the role in the control of inflammation, this function is exercised by inhibiting (nuclear factor kappa B) NF-κB, and also the genes that encode the expression of molecules with a pro-inflammatory role (cytokines and metalloproteinases). The other effects of CBD on cognitive function and physical performance should not be excluded. In conclusion, the CBD market needs to be regulated more thoroughly, given the previously listed properties, with the mention that the safety profile is a very good one.
... Our conceptual framework incorporates additional non-GPR55-dependent actions, such as a role for CBD reducing excitability via direct effects on ion channels, [25][26][27] and direct effects of CBD on the synthetic enzyme that produces LPI, PLA2. 65,66 Non-GPR55 targets might explain why CBD reduced seizure-induced mortality in both WT and GPR55 KO mice ( Figure 1D) and exerted effects on GABA A Rs above that of GPR55 knockdown alone ( Figure 5A), as if CBD also acted directly on GABA A Rs. 67 Further candidates for CBD's anti-seizure effects 17,18 include transient receptor potential (TRP) channel (TRPV1, TRPV2, and TRPA1) agonism, 68-71 CB 1 R negative allosteric modulation, 19,20 as well as inhibition of ENT-1 adenosine transporter, 72 CaV3.3 channels, 73 mitochondrial VDAC1 channels, 74 and regulation of non-neuronal cells (e.g., glia). In addition, GPR55 could also play a non-synaptic role in regulating ion channel conductances in interneurons, 16 especially PV+ interneurons 15,16,75 through effects of Na V channels. ...
Cannabidiol (CBD), a non-euphoric component of cannabis, reduces seizures in multiple forms of pediatric epilepsies, but the mechanism(s) of anti-seizure action remain unclear. In one leading model, CBD acts at glutamatergic axon terminals, blocking the pro-excitatory actions of an endogenous membrane phospholipid, lysophosphatidylinositol (LPI), at the G-protein-coupled receptor GPR55. However, the impact of LPI-GPR55 signaling at inhibitory synapses and in epileptogenesis remains underexplored. We found that LPI transiently increased hippocampal CA3-CA1 excitatory presynaptic release probability and evoked synaptic strength in WT mice, while attenuating inhibitory postsynaptic strength by decreasing GABAARγ2 and gephyrin puncta. LPI effects at excitatory and inhibitory synapses were eliminated by CBD pre-treatment and absent after GPR55 deletion. Acute pentylenetrazole-induced seizures elevated GPR55 and LPI levels, and chronic lithium-pilocarpine-induced epileptogenesis potentiated LPI's pro-excitatory effects. We propose that CBD exerts potential anti-seizure effects by blocking LPI's synaptic effects and dampening hyperexcitability.
... There are many additional modes of action that could be involved in the anti-seizure effects of CBD. For example, we have shown that CBD behaves as a positive allosteric modulator (PAM) of GABA A receptors [34,35], which could explain inhibition of neuronal excitability and reduced seizures. This mechanism is also shared by the phytocannabinoid cannabigerolic acid, which we recently showed to display anticonvulsant properties in Scn1a +/mice [36]. ...
A purified preparation of cannabidiol (CBD), a cannabis constituent, has been approved for the treatment of intractable childhood epilepsies such as Dravet syndrome. Extensive pharmacological characterization of CBD shows activity at numerous molecular targets but its anticonvulsant mechanism(s) of action is yet to be delineated. Many suggest that the anticonvulsant action of CBD is the result of G protein-coupled receptor 55 (GPR55) inhibition. Here we assessed whether Gpr55 contributes to the strain-dependent seizure phenotypes of the Scn1a +/- mouse model of Dravet syndrome. The Scn1a +/- mice on a 129S6/SvEvTac (129) genetic background have no overt phenotype, while those on a [129 x C57BL/6J] F1 background exhibit a severe phenotype that includes hyperthermia-induced seizures, spontaneous seizures and reduced survival. We observed greater Gpr55 transcript expression in the cortex and hippocampus of mice on the seizure-susceptible F1 background compared to those on the seizure-resistant 129 genetic background, suggesting that Gpr55 might be a genetic modifier of Scn1a +/- mice. We examined the effect of heterozygous genetic deletion of Gpr55 and pharmacological inhibition of GPR55 on the seizure phenotypes of F1. Scn1a +/- mice. Heterozygous Gpr55 deletion and inhibition of GPR55 with CID2921524 did not affect the temperature threshold of a thermally-induced seizure in F1. Scn1a +/- mice. Neither was there an effect of heterozygous Gpr55 deletion observed on spontaneous seizure frequency or survival of F1. Scn1a +/- mice. Our results suggest that GPR55 antagonism may not be a suitable anticonvulsant target for Dravet syndrome drug development programs, although future research is needed to provide more definitive conclusions.
... CBD also acts on various non-endocannabinoid receptors (Table I), including but not limited to G protein-coupled receptors (GPR3, GPR6, GPR12, GPR55) [22,[29][30][31][32], transient receptor potential channels (TRPM8, TRPA1, TRPV1, TRPV2) [27,[33][34][35][36], serotonin receptors [37,38], mu-and delta-opioid receptors [39,40], peroxisome proliferator-activated receptor gamma [41][42][43], and glycine receptors [44,45]. CBD was shown to act as a positive allosteric modulator of the inhibitory GABA A receptor and that its effects on potentiating this channel were complementary to the effects of the benzodiazepine and anticonvulsant clobazam [46,47]. Interaction with multiple receptors leads to future discovery and potential therapeutic use of CBD in different CNS conditions [39,48] (Table I). ...
The use of cannabidiol (CBD) for treating brain disorders has gained increasing interest. While the mechanism of action of CBD in these conditions is still under investigation, CBD has been shown to affect numerous different drug targets in the brain that are involved in brain disorders. Here we review the preclinical and clinical evidence on the potential therapeutic use of CBD in treating various brain disorders. Moreover, we also examine various drug delivery approaches that have been applied to CBD. Due to the slow absorption and low bioavailability with the current oral CBD therapy, more efficient routes of administration to bypass hepatic metabolism, particularly pulmonary delivery, should be considered. Comparison of pharmacokinetic studies of different delivery routes highlight the advantages of intranasal and inhalation drug delivery over other routes of administration (oral, injection, sublingual, buccal, and transdermal) for treating brain disorders. These two routes of delivery, being non-invasive and able to achieve fast absorption and increase bioavailability, are attracting increasing interest for CBD applications, with more research and development expected in the near future.
... Cannabidiol binds to the 5HT 1A receptor with moderate affinity and possesses agonist efficacy in 5HT 1A signal transduction studies [71]. Cannabidiol has also been shown to act as a positive allosteric modulator at GABA A receptors [72]. Cannabidiol's ability to enhance endocannabinoid levels and facilitate GABAergic transmission may serve to improve the balance in inhibitory and excitatory transmission and help restore neuronal function and synaptic plasticity in patients with FXS. ...
Multiple lines of evidence suggest a central role for the endocannabinoid system (ECS) in the neuronal development and cognitive function and in the pathogenesis of fragile X syndrome (FXS). This review describes the ECS, its role in the central nervous system, how it is dysregulated in FXS, and the potential role of cannabidiol as a treatment for FXS. FXS is caused by deficiency or absence of the fragile X messenger ribonucleoprotein 1 (FMR1) protein, FMRP, typically due to the presence of >200 cytosine, guanine, guanine sequence repeats leading to methylation of the FMR1 gene promoter. The absence of FMRP, following FMR1 gene-silencing, disrupts ECS signaling, which has been implicated in FXS pathogenesis. The ECS facilitates synaptic homeostasis and plasticity through the cannabinoid receptor 1, CB1, on presynaptic terminals, resulting in feedback inhibition of neuronal signaling. ECS-mediated feedback inhibition and synaptic plasticity are thought to be disrupted in FXS, leading to overstimulation, desensitization, and internalization of presynaptic CB1 receptors. Cannabidiol may help restore synaptic homeostasis by acting as a negative allosteric modulator of CB1, thereby attenuating the receptor overstimulation, desensitization, and internalization. Moreover, cannabidiol affects DNA methylation, serotonin 5HT1A signal transduction, gamma-aminobutyric acid receptor signaling, and dopamine D2 and D3 receptor signaling, which may contribute to beneficial effects in patients with FXS. Consistent with these proposed mechanisms of action of cannabidiol in FXS, in the CONNECT-FX trial the transdermal cannabidiol gel, ZYN002, was associated with improvements in measures of social avoidance, irritability, and social interaction, particularly in patients who are most affected, showing ≥90% methylation of the FMR1 gene.
... Other possible molecular targets of CBD have been also investigated. In particular, CBD can exert pharmacological effects through many receptors such as adenosine, glycine, opioid, serotonin, non-endocannabinoid G proteincoupled, nicotinic acetylcholine and peroxisome proliferator-activated receptors [27][28][29][30][31]. Recently, it has been observed that cannabidiol directly influences the functional properties of a number of ion channels, including Na v , K v , Ca v , and BK Ca [32,33]. ...
... Cannabidiol binds to the 5HT 1A receptor with moderate affinity and possesses agonist efficacy in 5HT 1A signal transduction studies [37]. Cannabidiol has also been shown to act as a positive allosteric modulator at GABA A receptors [38]. Cannabidiol's ability to enhance EC levels and facilitate GABAergic transmission may serve to improve the balance in inhibitory and excitatory transmission and help restore neuronal function and synaptic plasticity in patients with FXS. ...
Background
Fragile X syndrome (FXS) is associated with dysregulated endocannabinoid signaling and may therefore respond to cannabidiol therapy.
Design
CONNECT-FX was a double-blind, randomized phase 3 trial assessing efficacy and safety of ZYN002, transdermal cannabidiol gel, for the treatment of behavioral symptoms in children and adolescents with FXS.
Methods
Patients were randomized to 12 weeks of ZYN002 (250 mg or 500 mg daily [weight-based]) or placebo, as add-on to standard of care. The primary endpoint assessed change in social avoidance (SA) measured by the Aberrant Behavior Checklist–Community Edition FXS (ABC-C FXS ) SA subscale in a full cohort of patients with a FXS full mutation, regardless of the FMR1 methylation status. Ad hoc analyses assessed efficacy in patients with ≥ 90% and 100% methylation of the promoter region of the FMR1 gene, in whom FMR1 gene silencing is most likely.
Results
A total of 212 patients, mean age 9.7 years, 75% males, were enrolled. A total of 169 (79.7%) patients presented with ≥ 90% methylation of the FMR1 promoter and full mutation of FMR1 . Although statistical significance for the primary endpoint was not achieved in the full cohort, significant improvement was demonstrated in patients with ≥ 90% methylation of FMR1 (nominal P = 0.020). This group also achieved statistically significant improvements in Caregiver Global Impression‐Change in SA and isolation, irritable and disruptive behaviors, and social interactions (nominal P -values: P = 0.038, P = 0.028, and P = 0.002). Similar results were seen in patients with 100% methylation of FMR1 . ZYN002 was safe and well tolerated. All treatment-emergent adverse events (TEAEs) were mild or moderate. The most common treatment-related TEAE was application site pain (ZYN002: 6.4%; placebo: 1.0%).
Conclusions
In CONNECT-FX, ZYN002 was well tolerated in patients with FXS and demonstrated evidence of efficacy with a favorable benefit risk relationship in patients with ≥ 90% methylation of the FMR1 gene, in whom gene silencing is most likely, and the impact of FXS is typically most severe.
Trial registration
The CONNECT-FX trial is registered on Clinicaltrials.gov (NCT03614663).
... Overall, the reports suggest that CBD is effective against anxiety [45,46], psychotic symptoms [47,48], depression [49,50] and PTSD [51]. Furthermore, CBD is also effective in many pathological processes that are involved in the neurobiology of psychiatric disorders, such as neurodegeneration and impaired neuroplasticity [52,53], neuroinflammation [54,55], imbalanced neurotransmitter levels [56][57][58] and synaptic homeostasis [18,59]. Interestingly, these changes are under the control of transcriptional regulation involving changes in DNAm [60][61][62][63][64]. ...
Cannabidiol (CBD) is a non-psychotomimetic compound present in cannabis sativa. Many recent studies have indicated that CBD has a promising therapeutic profile for stress-related psychiatric disorders, such as anxiety, schizophrenia and depression. Such a diverse profile has been associated with its complex pharmacology, since CBD can target different neurotransmitter receptors, enzymes, transporters and ion channels. However, the precise contribution of each of those mechanisms for CBD effects is still not yet completely understood. Considering that epigenetic changes make the bridge between gene expression and environment interactions, we review and discuss herein how CBD affects one of the main epigenetic mechanisms associated with the development of stress-related psychiatric disorders: DNA methylation (DNAm). Evidence from in vivo and in silico studies indicate that CBD can regulate the activity of the enzymes responsible for DNAm, due to directly binding to the enzymes and/or by indirectly regulating their activities as a consequence of neurotransmitter-mediated signaling. The implications of this new potential pharmacological target for CBD are discussed in light of its therapeutic and neurodevelopmental effects.
... These channels are present on a wide range of cell types and can activate downstream calcium signaling, promoting apoptosis. CBD is also an allosteric regulator of ligand gated ion channels in the GABAa family and an inhibitor of calcium/sodium gated ion channels in the micromolar to the nanomolar range [34,35]. The distribution of CBD receptor expression within the body is depicted in Figure 1 [36]. ...
There is currently a growing interest in the use of cannabidiol (CBD) to alleviate the symptoms caused by cancer, including pain, sleep disruption, and anxiety. CBD is often self-administered as an over-the-counter supplement, and patients have reported benefits from its use. However, despite the progress made, the mechanisms underlying CBD’s anti-cancer activity remain divergent and unclear. Herein, we provide a comprehensive review of molecular mechanisms to determine convergent anti-cancer actions of CBD from pre-clinical and clinical studies. In vitro studies have begun to elucidate the molecular targets of CBD and provide evidence of CBD’s anti-tumor properties in cell and mouse models of cancer. Furthermore, several clinical trials have been completed testing CBD’s efficacy in treating cancer-related pain. However, most use a mixture of CBD and the psychoactive, tetrahydrocannabinol (THC), and/or use variable dosing that is not consistent between individual patients. Despite these limitations, significant reductions in pain and opioid use have been reported in cancer patients using CBD or CBD+THC. Additionally, significant improvements in quality-of-life measures and patients’ overall satisfaction with their treatment have been reported. Thus, there is growing evidence suggesting that CBD might be useful to improve the overall quality of life of cancer patients by both alleviating cancer symptoms and by synergizing with cancer therapies to improve their efficacy. However, many questions remain unanswered regarding the use of CBD in cancer treatment, including the optimal dose, effective combinations with other drugs, and which biomarkers/clinical presentation of symptoms may guide its use.
... 42 More recently, multiple studies have demonstrated the potential role of cannabinoids in activating the membrane ion channels, specifically transient receptor potential channels (TRP). 43,44 ...
For decades, chronic pain was managed with an almost conventional approach of using a
wide range of analgesic spectrum, surgical approaches and complex interventional pain
techniques to modulate or even interrupt pain pathways. These different approaches
carry many pharmacological hazards together with the lack of efficacy and safety of many
interventional and surgical management techniques for chronic pain have mandated
searching for other effective therapies including alternative treatments. Cannabinoids are
naturally occurring substances that are derived from Cannabis sativa L. The usage of
cannabinoids and their related synthetic chemical compounds has emerged as a choice in
the management of different chronic pain conditions is being evaluated, however, the
efficacy is still not consistently established. In the present investigation, therefore, we
discuss the different aspects related to cannabinoids and their implications in the
management of chronic pain conditions. This review will also discuss the safety profile of
the cannabinoids together with the legal considerations that hinder their use in different
countries.
... The copyright holder for this preprint this version posted September 28, 2022. ; https://doi.org/10.1101/2022.09.27.509638 doi: bioRxiv preprint 1D) and exerted effects on GABAARs above that of GPR55 knockdown alone (Fig. 5A), suggesting potential direct effects of CBD on GABAARs (Bakas et al., 2017). Further candidates for CBD's anti-seizure effects (Gray and Whalley, 2020;Ibeas Bih et al., 2015) include agonism of transient receptor potential (TRP) channels (TRPV1, TRPV2, TRPA1) (Bisogno et al., 2001;Costa et al., 2004;De Petrocellis et al., 2011;Qin et al., 2008), negative allosteric modulation of CB1Rs (Laprairie et al., 2015;Straiker et al., 2018), as well as inhibition of the ENT-1 transporter of adenosine (Carrier et al., 2006), CaV3.3 channels (Ross et al., 2008), mitochondrial VDAC1 channels (Rimmerman et al., 2013), and regulation of non-neuronal cells (e.g. ...
Cannabidiol (CBD), a non-euphoric component of cannabis, reduces seizures in multiple forms of pediatric epilepsy, but the mechanism(s) of anti-seizure action remain unclear. In one leading model, CBD acts at glutamatergic axon terminals, blocking pro-excitatory actions of an endogenous membrane phospholipid, lysophosphatidylinositol (LPI), at the G protein-coupled receptor GPR55. However, the impact of LPI-GPR55 signaling at inhibitory synapses and in epileptogenesis remains underexplored. We found that LPI transiently increased hippocampal CA3 to CA1 excitatory presynaptic release probability and evoked synaptic strength in WT mice, while attenuating inhibitory postsynaptic strength by decreasing GABAAR gamma 2 and gephyrin puncta. Effects of LPI at both excitatory and inhibitory synapses were eliminated by CBD pretreatment and absent after GPR55 deletion. Acute pentylenetrazole-induced seizures elevated levels of GPR55 and LPI, and chronic lithium pilocarpine-induced epileptogenesis potentiated the pro-excitatory effects of LPI. We propose that CBD exerts potential therapeutic effect both by blocking synaptic effects of LPI and dampening hyperexcitability.
Introdução: Os transtornos psiquiátricos, principalmente ansiedade e depressão, são queixas muito prevalentes na população mundial. Atualmente, esse fato move a comunidade científica a realizar estudos para avaliar alternativas que possam contribuir no tratamento dessas doenças. Por isso, a Cannabis Medicinal (CM) vem ganhando espaço na sociedade e parece ser uma opção terapêutica viável e vantajosa. Objetivo: Evidenciar os possíveis usos terapêuticos dos componentes presentes na planta Cannabis no manejo da ansiedade e depressão. Métodos: Trata-se de uma revisão bibliográfica integrativa, elaborada a partir de trabalhos científicos acerca da ação da Cannabis Medicinal como uma alternativa para o tratamento da ansiedade e depressão. Foram considerados artigos originais e completos publicados em português, espanhol e inglês nos últimos dez anos, de 2013 até 2023, obtidos nas plataformas SCIELO, PUBMED e LILACS. Resultados: As substâncias presentes na planta Cannabis, principalmente o Canabidiol (CBD), parecem ser uma opção promissora e potencialmente benéfica, especialmente para os casos que não respondem aos tratamentos convencionais. Conclusão: A partir dos estudos analisados, evidencia-se que os estudos atuais disponíveis sobre a eficácia dos canabinoides no tratamento dos transtornos mentais são de qualidade variável. Sendo assim, apesar da CM ser uma possível opção para o tratamento de transtornos mentais, ainda se faz necessária a realização de mais pesquisas para elucidar plenamente como funcionaria sua utilização na prática clínica.
Chronic neuropathic pain is a debilitating pain syndrome caused by damage to the nervous system that is poorly served by current medications. Given these problems, clinical studies have pursued extracts of the plant Cannabis sativa as alternative treatments for this condition. The vast majority of these studies have examined cannabinoids which contain the psychoactive constituent delta‐9‐tetrahydrocannabinol (THC). While there have been some positive findings, meta‐analyses of this clinical work indicates that this effectiveness is limited and hampered by side‐effects. This review focuses on how recent preclinical studies have predicted the clinical limitations of THC‐containing cannabis extracts, and importantly, point to how they might be improved. This work highlights the importance of targeting channels and receptors other than cannabinoid CB1 receptors which mediate many of the side‐effects of cannabis. image
The ‘entourage effect’ term was originally coined in a pre-clinical study observing endogenous bio-inactive metabolites potentiating the activity of a bioactive endocannabinoid. As a hypothetical afterthought, this was proposed to hold general relevance to the usage of products based on Cannabis sativa L. The term was later juxtaposed to polypharmacy pertaining to full-spectrum medicinal Cannabis products exerting an overall higher effect than the single compounds. Since the emergence of the term, a discussion of its pharmacological foundation and relevance has been ongoing. Advocates suggest that the ‘entourage effect’ is the reason many patients experience an overall better effect from full-spectrum products. Critics state that the term is unfounded and used primarily for marketing purposes in the Cannabis industry. This scoping review aims to segregate the primary research claiming as well as disputing the existence of the ‘entourage effect’ from a pharmacological perspective. The literature on this topic is in its infancy. Existing pre-clinical and clinical studies are in general based on simplistic methodologies and show contradictory findings, with the clinical data mostly relying on anecdotal and real-world evidence. We propose that the ‘entourage effect’ is explained by traditional pharmacological terms pertaining to other plant-based medicinal products and polypharmacy in general (e.g., synergistic interactions and bioenhancement).
Abstract
Cannabis sativa contains phytocannabinoids that are psychoactive and neurotoxic (delta-9-tetrahydrocannabinol: Δ9THC) or
nonpsychoactive and presumptively neuroprotective (cannabidiol: CBD). Along with rising legalization, availability, and
demand, the Δ9THC:CBD ratio also has increased. Cannabis legalization means that use will likely increase in pregnant or
breastfeeding women, affecting all stages of brain and neurodevelopment of their offspring. Δ9THC exposure in utero or during
development leads to lasting detrimental effects on behavior, cognition, locomotor activity, as well as epigenetic changes.
Caution is urged with cannabis use. CBD is one of the most actively studied therapies for a broad spectrum of neurological,
inflammatory, and mental diseases (e.g., Parkinson’s disease, Huntington’s disease, Alzheimer’s disease, schizophrenia) because
of its efficacy, low toxicity, and availability. While data indicate that the benefits of CBD may outweigh its risks, there are
indications that it poses a risk for adverse effects on neurodevelopment from in-utero exposure as well as detrimental effects on
male reproduction. Therefore, there is a clear need to continue researching the effects of Δ9THC exposure as well as the optimal
CBD treatment related to disease management while stressing the need to further characterize possible adverse effects.
An updated third edition of this award-winning book provides a comprehensive overview of the complex associations between cannabis and mental illness. Organised into easy to navigate sections, the book has been fully revised to feature eight entirely new chapters covering important novel aspects. Marijuana and Madness incorporates new research findings on the potential use of cannabinoids, and synthetic cannabinoids, in an array of mental illnesses, balanced against the potential adverse effects. The associations between cannabis and psychosis, developing putative models of 'cannabis induced' psychosis and pathways to schizophrenia are all covered. The book importantly discusses the impact of exposure to cannabis at various stages of neurodevelopment (in utero, in childhood, and during adolescence) and it thoroughly reviews the treatments for cannabis dependence and health policy implications of the availability of increasingly high potency cannabis. This book will quickly become an essential resource for all members of the mental health team.
The cannabis derivative marijuana is the most widely used recreational drug in the Western world, that is consumed by an estimated 83 million individuals (~3% of the world population). In recent years, there has been a marked transformation in society regarding the risk perception of cannabis, driven by its legalization and medical use in many states in the USA and worldwide. Compelling research evidence and the FDA cannabis-derived cannabidiol approval for severe childhood epilepsy have confirmed the large therapeutic potential of cannabidiol itself, Δ9-tetrahydrocannabinol (THC) and other plant-derived cannabinoids (phytocannabinoids). Of note, our body has a complex endocannabinoid system (ECS) - made of receptors, metabolic enzymes and transporters - that is also regulated by phytocannabinoids. The first endocannabinoid to be discovered 30 years ago was anandamide (N-arachidonoyl-ethanolamine); since then, distinct elements of ECS have been the target of drug design programs aimed at curing (or at least slowing down) a number of human diseases, both in the central nervous system and at the periphery. Here, a critical review of our knowledge of the goods and bads of ECS as a therapeutic target are presented, in order to define the benefits of ECS-active phytocannabinoids and ECS-oriented synthetic drugs for human health. Significance Statement The endocannabinoid system plays important roles everywhere in our body and is either involved in mediating key processes of central and peripheral diseases or represents a therapeutic target for treatment. Understanding structure, function, and pharmacology of the components of this complex system, and in particular of key receptors (like CB1R and CB2R) and metabolic enzymes (like FAAH and MAGL), will advance our understanding of endocannabinoid signaling and activity at molecular, cellular, and system levels providing new opportunities to treat patients.
Despite the wide range of compounds currently available to treat epilepsy, there is still no drug that directly tackles the physiopathological mechanisms underlying its development. Indeed, antiseizure medications attempt to prevent seizures but are inefficacious in counteracting or rescuing the physiopathological phenomena that underlie their onset and recurrence, and hence do not cure epilepsy. Classically, the altered excitation/inhibition balance is postulated as the mechanism underlying epileptogenesis and seizure generation. This oversimplification, however, does not account for deficits in homeostatic plasticity resulting from either insufficient or excessive compensatory mechanisms in response to a change in network activity. In this respect, both neurodevelopmental epilepsies and those associated with neurodegeneration may share common underlying mechanisms that still need to be fully elucidated. The understanding of these molecular mechanisms shed light on the identification of new classes of drugs able not only to suppress seizures, but also to present potential antiepileptogenic effects or "disease-modifying" properties.
Background:
Cannabidiol (CBD) is one of the main phytocannabinoids found in Cannabis sativa. In contrast to Δ9-tetrahydrocannabinol, it has a low affinity for cannabinoid receptors CB1 and CB2, thereby it does not induce significant psychoactive effects. However, CBD may interact with other receptors, including peroxisome proliferator-activated receptor gamma (PPARγ). CBD is a PPARγ agonist and changes its expression. There is considerable evidence that CBD's effects are mediated by its interaction with PPARγ. So, we reviewed studies related to the interaction of CBD and PPARγ.
Methods:
In this comprehensive literature review, the term 'cannabidiol' was used in combination with the following keywords including 'PPARγ', 'Alzheimer's disease', 'Parkinson's disease', 'seizure', 'multiple sclerosis', 'immune system', 'cardiovascular system', 'cancer', and 'adipogenesis'. PubMed, Web of Science, and Google Scholar were searched until December 20, 2022. A total of 78 articles were used for the reviewing process.
Results:
CBD, via activation of PPARγ, promotes significant pharmacological effects. The present review shows that the effects of CBD on Alzheimer's disease and memory, Parkinson's disease and movement disorders, multiple sclerosis, anxiety and depression, cardiovascular system, immune system, cancer, and adipogenesis are mediated, at least in part, via PPARγ.
Conclusion:
CBD not only activates PPARγ but also affects its expression in the body. It was suggested that the late effects of CBD are mediated via PPARγ activation. We suggested that CBD's chemical structure is a good backbone for developing new dual agonists. Combining it with other chemicals enhances their biological effectiveness while reducing their dosage. The present study indicated that PPARγ is a key target for CBD, and its activation by CBD should be considered in all future studies.
Cannabidiol (CBD) has numerous pharmacological targets that initiate anti-inflammatory, antioxidative, and antiepileptic properties. These neuroprotective benefits have generated interest in CBD's therapeutic potential against the secondary injury cascade from traumatic brain injury (TBI). There are currently no effective broad treatment strategies for combating the damaging mechanisms that follow the primary injury and lead to lasting neurological consequences or death. However, CBD's effects on different neurotransmitter systems, the blood brain barrier, oxidative stress mechanisms, and the inflammatory response provides mechanistic support for CBD's clinical utility in TBI. This review describes the cascades of damage caused by TBI and CBD's neuroprotective mechanisms to counter them. We also present challenges in the clinical treatment of TBI and discuss important future clinical research directions for integrating CBD in treatment protocols. The mechanistic evidence provided by pre-clinical research shows great potential for CBD as a much-needed improvement in the clinical treatment of TBI. Upcoming clinical trials sponsored by major professional sport leagues are the first attempts to test the efficacy of CBD in head injury treatment protocols and highlight the need for further clinical research.
Epilepsy is a common neurological disorder associated with alterations of excitation‐inhibition balance within brain neuronal networks. GABAA receptor neurotransmission is the most prevalent form of inhibitory neurotransmission and is strongly implicated in both the pathophysiology and treatment of epilepsy, serving as a primary target for antiseizure medications for over a century. It is now established that GABA exerts a multifaceted influence through an array of GABAA receptor subtypes that extends far beyond simply negating excitatory activity. As the role of GABAA neurotransmission within inhibitory circuits is elaborated, this will enable the development of precision therapies that correct the network dysfunction underlying epileptic pathology.
Δ9-tetrahydrocannabinol (THC) and its sibling, cannabidiol (CBD), are produced by the same Cannabis plant and have similar chemical structures but differ dramatically in their mechanisms of action and effects on brain functions. Both THC and CBD exhibit promising therapeutic properties; however, impairments and increased incidence of mental health diseases are associated with acute and chronic THC use, respectively, and significant side effects are associated with chronic use of high-dose CBD. This review covers recent molecular and preclinical discoveries concerning the distinct mechanisms of action and bioactivities of THC and CBD and their impact on human behavior and diseases. These discoveries provide a foundation for the development of cannabinoid-based therapeutics for multiple devastating diseases and to assure their safe use in the growing legal market of Cannabis-based products.
Epilepsy is a serious neurological disorder associated with recurrent and unpredictable seizures and extensive neuropsychiatric comorbidities. There is no cure for epilepsy, and over one third of epileptic patients have been diagnosed with drug-refractory epilepsy, indicating the critical need for novel antiseizure medications (ASMs). Cannabidiol (CBD) has been shown to decrease seizures in pediatric epilepsies, such as Dravet and Lennox-Gastaut syndromes; however, it has not been rigorously tested for adult seizures or in models of refractory focal epilepsy. Although the exact mechanism is unknown, it is likely to act in a way that is unique to certain GABA-A receptor-modulating drugs, such as neurosteroids and benzodiazepines. In this study, we sought to determine the adjunct antiseizure activity of a clinical CBD product in an adult 6-Hz model of focal refractory epilepsy. CBD was evaluated alone in both a dose-response and time-course manner and in an adjunct combination with two ASMs ganaxolone (neurosteroid) and midazolam (benzodiazepine) against 6-Hz-induced refractory focal onset, generalized seizures. In pharmacological studies, CBD produced dose-dependent protection against seizures (ED50, 53 mg/kg, i.p.) without any side effects. CBD significantly reduced both electrographic activity and behavioral ictal responses with no apparent sex differences. CBD was evaluated in an isobologram design in conjunction with ganaxolone or midazolam at three standard ratios (1:1, 1:3, 3:1). Isobolographic analysis shows the combination regimens of CBD + ganaxolone and CBD+ midazolam exerted combination index of 0.313 and 0.164, indicating strong synergism for seizure protection, with little to no toxicity. Together, these results demonstrate the therapeutic potential of CBD monotherapy and as an adjunct therapy for adult focal refractory epilepsy in combination with GABAergic ASMs.
The management of refractory epilepsy involves treatment with more than one antiseizure medication (ASM). Combination of ASMs with distinct mechanisms of action are hypothesized to improve overall treatment effectiveness. In clinical trials, concomitant use of cannabidiol (CBD) and clobazam (CLB) was associated with increased seizure reduction and bidirectional elevation in levels of their active metabolites, 7-hydroxy-cannabidiol (7-OH-CBD) and nor-clobazam (n-CLB). Using isobolographic analysis, we investigated whether CBD and CLB interacted pharmacodynamically. In the mouse maximal electroshock seizure (MES) test, brain tissue levels of CBD and CLB corresponding to seizure prevention in 50% of animals (brain Effective Exposure, bEE50) were 7.9 μM and 1.6 μM, respectively. In the 6 Hz psychomotor seizure model, 7-OH-CBD displayed a 5-fold greater potency than CBD (b-EE50, 8.7 μM vs 47.3 μM). Isobolographic analysis performed on combination of CBD/CLB at 1:1, 3:1, and 1:3 ratios based on equi-effective bEE50 values revealed synergism at all doses with combination indices (CI) of 0.43, 0.62 and 0.75 respectively. These outcomes were independent of pharmacokinetic interaction between CBD and CLB. These findings identify pharmacodynamic synergism as an important factor underlying enhanced antiseizure effect during concomitant CBD and CLB use.
Introduction
Cannabis is an increasingly popular recreational and medicinal drug in the USA. While cannabis is still a Schedule 1 drug federally, many states have lifted the ban on its use. With its increased usage, there is an increased potential for potential drug-drug interactions (DDI) that may occur with concomitant use of cannabis and pharmaceuticals.
Area covered
This review focuses on the current knowledge of cannabis induced DDI, with a focus on pharmacokinetic DDI arising from enzyme inhibition or induction. Phase I and phase II drug metabolizing enzymes, specifically cytochromes P450, carboxylesterases, and uridine-5’-diphosphoglucuronosyltransferases, have historically been the focus of research in this field, with the much of the current knowledge of the potential for cannabis to induce DDI within these families of enzymes coming from in vitro enzyme inhibition studies. Together with a limited number of in vivo clinical studies and in silico investigations, current research suggests that cannabis exhibits the potential to induce DDI under certain circumstances.
Expert opinion
Based upon the current literature, there is a strong potential for cannabis-induced DDI among major drug-metabolizing enzymes.
The cover image is based on the Original Article Phytocannabinoids regulate inflammation in IL‐1β‐stimulated human gingival fibroblasts by Ammaar H. Abidi et al., https://doi.org/10.1111/jre.13050
Background
A prior drug trial of cannabidiol for treatment- resistant epilepsy in patients with Sturge-Weber syndrome, a rare neurovascular condition, implicated improvements in neurologic, quality of life, neuropsychological, psychiatric, and motor outcomes.
Methods
Ten subjects with SWS brain involvement, controlled seizures, and cognitive impairments received study drug in this Johns Hopkins IRB approved, open-label, prospective drug trial. Oral cannabidiol was taken for six months (dose ranged from 5 mg/kg/day to 20 mg/kg/day). SWS neuroscore, port-wine birthmark score, quality of life, and adverse events were recorded every 4-12 weeks. Neuropsychological, psychiatric, and motor assessments were administered at baseline and six months follow-up. Most evaluations were conducted virtually due to the COVID-19 pandemic.
Results
Cannabidiol was generally well tolerated. Six subjects reported mild to moderate side effects related to study drug and continued on drug; one subject withdrew early due to moderate side effects. No seizures were reported. Significant improvements in SWS neuroscore, patient- reported quality of life (QOL), anxiety and emotional regulation, and report of bimanual ability use, were noted. Migraine QOL scores were high at baseline in these subjects, and remained high. Neuropsychological, other quality of life and motor outcomes remained stable, with some within subject improvements noted.
Conclusions
Further studies are needed to determine whether Epidiolex can improve quality of life and be beneficial for neurologic, anxiety, and motor impairments in SWS independent of seizure control. Large multi-centered studies are needed to extend these preliminary findings.
Endocannabinoids (eCBS) are endogenously derived lipid signaling molecules that serve as tissue hormones and interact with multiple targets, mostly within the endocannabinoid system (ECS). The ECS is a highly conserved regulatory system involved in homeostatic regulation, organ formation, and immunomodulation of chordates. The term “cannabinoid” evolved from the distinctive class of plant compounds found in Cannabis sativa, an ancient herb, due to their action on CB1 and CB2 receptors. CB1/2 receptors are the primary targets for eCBs, but their effects are not limited to the ECS. Due to the high interest and extensive research on the ECS, knowledge on its constituents and physiological role is substantial and still growing. Crosstalk and multiple targeting of molecules are common features of endogenous and plant compounds. Cannabimimetic molecules can be divided according to their origin, natural or synthetic, including phytocannabinoids (pCB’s) or synthetic cannabinoids (sCB’s). The endocannabinoid system (ECS) consists of receptors, transporters, enzymes, and signaling molecules. In this review, we focus on the effects of cannabinoids on Cys-loop receptors. Cys-loop receptors belong to the class of membrane-bound pentameric ligand gated ion channels, each family comprising multiple subunits. Mammalians possess GABA type A receptors (GABAAR), glycine receptors (GlyR), serotonin receptors type 3 (5-HT3R), and nicotinic acetylcholine receptors (nAChR). Several studies have shown different modulatory effects of CBs on multiple members of the Cys-loop receptor family. We highlight the existing knowledge, especially on subunits and protein domains with conserved binding sites for CBs and their possible pharmacological and physiological role in epilepsy and in chronic pain. We further discuss the potential for cannabinoids as first line treatments in epilepsy, chronic pain and other neuropsychiatric conditions, indicated by their polypharmacology and therapeutic profile.
Novel and effective antiseizure medications are needed to treat refractory and rare forms of epilepsy. Cannabinoids, which are obtained from the cannabis plant, have a long history of medical use, including for neurologic conditions. In 2018, the US Food and Drug Administration approved the first phytocannabinoid, cannabidiol (CBD, Epidiolex®), which is now indicated for severe seizures associated with three rare forms of developmental and epileptic encephalopathy: Dravet syndrome, Lennox–Gastaut syndrome, and tuberous sclerosis complex. Compelling evidence supports the efficacy of CBD in experimental models and patients with epilepsy. In randomized clinical trials, highly-purified CBD has demonstrated efficacy with an acceptable safety profile in children and adults with difficult-to-treat seizures. Although the underlying antiseizure mechanisms of CBD in humans have not yet been elucidated, the identification of novel antiseizure targets of CBD preclinically indicates multimodal mechanisms that include non-cannabinoid pathways. In addition to antiseizure effects, CBD possesses strong anti-inflammatory and neuroprotective activities, which might contribute to protective effects in epilepsy and other conditions. This article provides a succinct overview of therapeutic approaches and clinical foundations of CBD, emphasizing the clinical utility of CBD for the treatment of seizures associated with refractory and rare epilepsies. CBD has shown to be a safe and effective antiseizure medicine, demonstrating a broad spectrum of efficacy across multiple seizure types, including those associated with severe epilepsies with childhood onset. Despite such promise, there are many perils with CBD that hampers its widespread use, including limited understanding of pharmacodynamics, limited exposure-response relationship, limited information for seizure freedom with continued use, complex pharmacokinetics with drug interactions, risk of adverse effects, and lack of expert therapeutic guidelines. These scientific issues need to be resolved by further investigations, which would decide the unique role of CBD in the management of refractory epilepsy.
Extracts of the pepper plant kava (Piper methysticum) are effective in alleviating anxiety in clinical trials. Despite the long-standing therapeutic interest in kava, the molecular target(s) of the pharmacologically active constituents, kavalactones have not been established. γ-Aminobutyric acid type A receptors (GABAARs) are assumed to be the in vivo molecular target of kavalactones based on data from binding assays, but evidence in support of a direct interaction between kavalactones and GABAARs is scarce and equivocal. In this study, we characterised the functional properties of the major anxiolytic kavalactone, kavain at human recombinant α1β2, β2γ2L, αxβ2γ2L (x = 1, 2, 3 and 5), α1βxγ2L (x = 1, 2 and 3) and α4β2δ GABAARs expressed in Xenopus oocytes using the two-electrode voltage clamp technique. We found that kavain positively modulated all receptors regardless of the subunit composition, but the degree of enhancement was greater at α4β2δ than at α1β2γ2L GABAARs. The modulatory effect of kavain was unaffected by flumazenil, indicating that kavain did not enhance GABAARs via the classical benzodiazepine binding site. The β3N265M point mutation which has been previously shown to profoundly decrease anaesthetic sensitivity, also diminished kavain-mediated potentiation. To our knowledge, this study is the first report of the functional characteristics of a single kavalactone at distinct GABAAR subtypes, and presents the first experimental evidence in support of a direct interaction between a kavalactone and GABAARs.
Cannabidiol (CBD) is currently being investigated as a novel therapeutic for the treatment of CNS disorders like schizophrenia and epilepsy. ABC transporters such as P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) mediate pharmacoresistance in these disorders. P-gp and Bcrp are expressed at the blood brain barrier (BBB) and reduce the brain uptake of substrate drugs including various antipsychotics and anticonvulsants. It is therefore important to assess whether CBD is prone to treatment resistance mediated by P-gp and Bcrp. Moreover, it has become common practice in the drug development of CNS agents to screen against ABC transporters to help isolate lead compounds with optimal pharmacokinetic properties. The current study aimed to assess whether P-gp and Bcrp impacts the brain transport of CBD by comparing CBD tissue concentrations in wild-type (WT) mice versus mice devoid of ABC transporter genes. P-gp knockout (
Abcb1a/b
−∕−
), Bcrp knockout (
Abcg2
−∕−
), combined P-gp/Bcrp knockout (
Abcb1a/b
−∕−
Abcg2
−∕−
) and WT mice were injected with CBD, before brain and plasma samples were collected at various time-points. CBD results were compared with the positive control risperidone and 9-hydroxy risperidone, antipsychotic drugs that are established ABC transporter substrates. Brain and plasma concentrations of CBD were not greater in P-gp, Bcrp or P-gp/Bcrp knockout mice than WT mice. In comparison, the brain/plasma concentration ratios of risperidone and 9-hydroxy risperidone were profoundly higher in P-gp knockout mice than WT mice. These results suggest that CBD is not a substrate of P-gp or Bcrp and may be free from the complication of reduced brain uptake by these transporters. Such findings provide favorable evidence for the therapeutic development of CBD in the treatment of various CNS disorders.
Agonists at the benzodiazepine-binding site of GABAA receptors (BDZs) enhance synaptic inhibition through four subtypes (α1, α2, α3 and α5) of GABAA receptors (GABAAR). When applied to the spinal cord, they alleviate pathological pain; however, insufficient efficacy after systemic administration and undesired effects preclude their use in routine pain therapy. Previous work suggested that subtype-selective drugs might allow separating desired antihyperalgesia from unwanted effects, but the lack of selective agents has hitherto prevented systematic analyses. Here we use four lines of triple GABAAR point-mutated mice, which express only one benzodiazepine-sensitive GABAAR subtype at a time, to show that targeting only α2GABAARs achieves strong antihyperalgesia and reduced side effects (that is, no sedation, motor impairment and tolerance development). Additional pharmacokinetic and pharmacodynamic analyses in these mice explain why clinically relevant antihyperalgesia cannot be achieved with nonselective BDZs. These findings should foster the development of innovative subtype-selective BDZs for novel indications such as chronic pain.
Based on evidence that the therapeutic properties of Cannabis preparations are not solely dependent on the presence of Δ9-tetrahydrocannabinol (THC), pharmacological studies have been recently carried out with other plant cannabinoids (phytocannabinoids), particularly cannabidiol (CBD) and Δ9-tetrahydrocannabivarin (THCV). Results from some of these studies have fostered the view that CBD and THCV modulate the effects of THC via direct blockade of cannabinoid type-1 (CB1) receptors, thus behaving like first generation CB1 inverse agonists, such as rimonabant. Here we review in vitro and ex vivo mechanistic studies of CBD and THCV, and synthesize data from these studies in a meta-analysis. Synthesized data regarding mechanisms are then used to interpret results from recent preclinical animal studies and clinical trials. The evidence indicates that CBD and THCV are not rimonabant-like in their action, and thus appear very unlikely to produce unwanted central nervous system effects. They exhibit markedly disparate pharmacological profiles particularly at CB1 receptors: CBD is a very low affinity CB1 ligand which can nevertheless affect CB1 activity in vivo in an indirect manner, whilst THCV is a high affinity CB1 ligand and potent antagonist in vitro and yet only occasionally produces effects in vivo resulting from CB1 antagonism. THCV also has high affinity for CB2 and signals as a partial agonist, a departure from both CBD and rimonabant. These cannabinoids illustrate how in vitro mechanistic studies do not always predict in vivo pharmacology, and underlie the necessity of testing compounds in vivo before drawing any conclusion on their functional activity at a given target.
Cannabidiol (CBD), a major phytocannabinoid constituent of cannabis, is attracting growing attention in medicine for its anxiolytic, antipsychotic, antiemetic and anti-inflammatory properties. However, up to this point, a comprehensive literature review of the effects of CBD in humans is lacking. The aim of the present systematic review is to examine the randomized and crossover studies that administered CBD to healthy controls and to clinical patients. A systematic search was performed in the electronic databases PubMed and EMBASE using the key word "cannabidiol". Both monotherapy and combination studies (e.g., CBD + ∆9-THC) were included. A total of 34 studies were identified: 16 of these were experimental studies, conducted in healthy subjects, and 18 were conducted in clinical populations, including multiple sclerosis (six studies), schizophrenia and bipolar mania (four studies), social anxiety disorder (two studies), neuropathic and cancer pain (two studies), cancer anorexia (one study), Huntington's disease (one study), insomnia (one study), and epilepsy (one study). Experimental studies indicate that a high-dose of inhaled/intravenous CBD is required to inhibit the effects of a lower dose of ∆9-THC. Moreover, some experimental and clinical studies suggest that oral/oromucosal CBD may prolong and/or intensify ∆9-THC-induced effects, whereas others suggest that it may inhibit ∆9-THC-induced effects. Finally, preliminary clinical trials suggest that high-dose oral CBD (150-600 mg/d) may exert a therapeutic effect for social anxiety disorder, insomnia and epilepsy, but also that it may cause mental sedation. Potential pharmacokinetic and pharmacodynamic explanations for these results are discussed.
Drugs that enhance GABAergic inhibition alleviate inflammatory and neuropathic pain after spinal application. This antihyperalgesia occurs mainly through GABAA receptors (GABAARs) containing α2 subunits (α2-GABAARs). Previous work indicates that potentiation of these receptors in the spinal cord evokes profound antihyperalgesia also after systemic administration, but possible synergistic or antagonistic actions of supraspinal α2-GABAARs on spinal antihyperalgesia have not yet been addressed. Here we generated two lines of GABAAR-mutated mice, which either lack α2-GABAARs specifically from the spinal cord, or, which express only benzodiazepine-insensitive α2-GABAARs at this site. We analyzed the consequences of these mutations for antihyperalgesia evoked by systemic treatment with the novel non-sedative benzodiazepine site agonist HZ166 in neuropathic and inflammatory pain. Wild-type mice and both types of mutated mice had similar baseline nociceptive sensitivities and developed similar hyperalgesia. However, antihyperalgesia by systemic HZ166 was reduced in both mutated mouse lines by about 60% and was virtually indistinguishable from that of global point-mutated mice, in which all α2-GABAARs were benzodiazepine insensitive. The major (α2-dependent) component of GABAAR-mediated antihyperalgesia was therefore exclusively of spinal origin, whereas supraspinal α2-GABAARs had neither synergistic nor antagonistic effects on antihyperalgesia. Our results thus indicate that drugs that specifically target α2-GABAARs exert their antihyperalgesic effect through enhanced spinal nociceptive control. Such drugs may therefore be well-suited for the systemic treatment of different chronic pain conditions.Neuropsychopharmacology advance online publication, 18 September 2013; doi:10.1038/npp.2013.221.
Owing to the low therapeutic index of barbiturates, benzodiazepines (BZDs) became popular in this country and worldwide many decades ago for a wide range of conditions. Because of an increased understanding of pharmacology and physiology, the mechanisms of action of many BZDs are now largely understood, and BZDs of varying potency and duration of action have been developed and marketed. Although BZDs have many therapeutic roles and BZD-mediated effects are typically well tolerated in the general population, side effects and toxicity can result in morbidity and mortality for some patients. The elderly; certain subpopulations of patients with lung, liver, or kidney dysfunction; and patients on other classes of medication are especially prone to toxicity.
This review details the present knowledge about BZD mechanisms of action, drug profiles, clinical actions, and potential side effects. In addition, this review describes numerous types of BZD-mediated central nervous system effects.
For any patient taking a BZD, the prescribing physician must carefully evaluate the risks and benefits, and higher-risk patients require careful considerations. Clinically appropriate use of BZDs requires prudence and the understanding of pharmacology.
Anandamide and 2-arachidonoylglycerol (2-AG) are the two main endocannabinoids, exerting their effects by activating type 1 (CB1r) and type 2 (CB2r) cannabinoid receptors. Anandamide inhibits anxiety-like responses through the activation of CB1r in certain brain regions, including the dorsolateral periaqueductal gray (dlPAG). 2-AG also attenuates anxiety-like responses, although the neuroanatomical sites for these effects remained unclear. Here, we tested the hypothesis that enhancing 2-AG signaling in the dlPAG would induce anxiolytic-like effects. The mechanisms involved were also investigated. Male Wistar rats received intra-dlPAG injections of 2-AG, URB602 (inhibitor of the 2-AG hydrolyzing enzyme, mono-acylglycerol lipase - MGL), AM251 (CB1r antagonist) and AM630 (CB2r antagonist). The behaviour was analyzed in the elevated plus maze after the following treatments. Exp. 1: vehicle (veh) or 2-AG (5pmol, 50pmol, 500pmol). Exp. 2: veh or URB602 (30pmol, 100pmol or 300pmol). Exp. 3: veh or AM251 (100pmol) followed by veh or 2-AG (50pmol). Exp. 4: veh or AM630 (1000pmol) followed by veh or 2-AG. Exp. 5: veh or AM251 followed by veh or URB602 (100pmol). Exp. 6: veh or AM630 followed by veh or URB602. 2-AG (50pmol) and URB602 (100pmol) significantly increased the exploration of the open arms of the apparatus, indicating an anxiolytic-like effect. These behavioral responses were prevented by CB1r (AM251) or CB2r (AM630) antagonists. Our results showed that the augmentation of 2-AG levels in the dlPAG induces anxiolytic-like effects. The mechanism seems to involve both CB1r and CB2r receptors.
Cannabidiol (CBD) is a major phytocannabinoid present in the Cannabis sativa plant. It lacks the psychotomimetic and other psychotropic effects that the main plant compound Δ(9)-tetrahydrocannabinol (THC) being able, on the contrary, to antagonize these effects. This property, together with its safety profile, was an initial stimulus for the investigation of CBD pharmacological properties. It is now clear that CBD has therapeutic potential over a wide range of non-psychiatric and psychiatric disorders such as anxiety, depression and psychosis. Although the pharmacological effects of CBD in different biological systems have been extensively investigated by in vitro studies, the mechanisms responsible for its therapeutic potential are still not clear. Here, we review recent in vivo studies indicating that these mechanisms are not unitary but rather depend on the behavioural response being measured. Acute anxiolytic and antidepressant-like effects seem to rely mainly on facilitation of 5-HT1A-mediated neurotransmission in key brain areas related to defensive responses, including the dorsal periaqueductal grey, bed nucleus of the stria terminalis and medial prefrontal cortex. Other effects, such as anti-compulsive, increased extinction and impaired reconsolidation of aversive memories, and facilitation of adult hippocampal neurogenesis could depend on potentiation of anandamide-mediated neurotransmission. Finally, activation of TRPV1 channels may help us to explain the antipsychotic effect and the bell-shaped dose-response curves commonly observed with CBD. Considering its safety profile and wide range of therapeutic potential, however, further studies are needed to investigate the involvement of other possible mechanisms (e.g. inhibition of adenosine uptake, inverse agonism at CB2 receptor, CB1 receptor antagonism, GPR55 antagonism, PPARγ receptors agonism, intracellular (Ca(2+)) increase, etc.), on CBD behavioural effects.
Δ 9-tetrahydrocannabinol (Δ 9-THC) is the main compound of the Cannabis Sativa responsible for most of the effects of the plant. Another major constituent is cannabidiol (CBD), formerly regarded to be devoid of pharmacological activity. However, laboratory rodents and human studies have shown that this cannabinoid is able to prevent psychotic-like symptoms induced by high doses of Δ 9- THC. Subsequent studies have demonstrated that CBD has antipsychotic effects as observed using animal models and in healthy volunteers. Thus, this article provides a critical review of the research evaluating antipsychotic potential of this cannabinoid. CBD appears to have pharmacological profile similar to that of atypical antipsychotic drugs as seem using behavioral and neurochemical techniques in animal models. Additionally, CBD prevented human experimental psychosis and was effective in open case reports and clinical trials in patients with schizophrenia with a remarkable safety profile. Moreover, fMRI results strongly suggest that the antipsychotic effects of CBD in relation to the psychotomimetic effects of Δ 9-THC involve the striatum and temporal cortex that have been traditionally associated with psychosis. Although the mechanisms of the antipsychotic properties are still not fully understood, we propose a hypothesis that could have a heuristic value to inspire new studies. These results support the idea that CBD may be a future therapeutic option in psychosis, in general and in schizophrenia, in particular.
Certain types of nonpsychoactive cannabinoids can potentiate glycine receptors (GlyRs), an important target for nociceptive regulation at the spinal level. However, little is known about the potential and mechanism of glycinergic cannabinoids for chronic pain treatment. We report that systemic and intrathecal administration of cannabidiol (CBD), a major nonpsychoactive component of marijuana, and its modified derivatives significantly suppress chronic inflammatory and neuropathic pain without causing apparent analgesic tolerance in rodents. The cannabinoids significantly potentiate glycine currents in dorsal horn neurons in rat spinal cord slices. The analgesic potency of 11 structurally similar cannabinoids is positively correlated with cannabinoid potentiation of the α3 GlyRs. In contrast, the cannabinoid analgesia is neither correlated with their binding affinity for CB1 and CB2 receptors nor with their psychoactive side effects. NMR analysis reveals a direct interaction between CBD and S296 in the third transmembrane domain of purified α3 GlyR. The cannabinoid-induced analgesic effect is absent in mice lacking the α3 GlyRs. Our findings suggest that the α3 GlyRs mediate glycinergic cannabinoid-induced suppression of chronic pain. These cannabinoids may represent a novel class of therapeutic agents for the treatment of chronic pain and other diseases involving GlyR dysfunction.
An attempt to find pharmacological therapies to treat stroke patients and minimize the extent of cell death has seen the failure of dozens of clinical trials. As a result, stroke/cerebral ischemia is the leading cause of lasting adult disability. Stroke-induced cell death occurs due to an excess release of glutamate. As a consequence to this, a compensatory increased release of GABA occurs that results in the subsequent internalization of synaptic GABA(A) receptors and spillover onto perisynaptic GABA(A) receptors, resulting in increased tonic inhibition. Recent studies show that the brain can engage in a limited process of neural repair after stroke. Changes in cortical sensory and motor maps and alterations in axonal structure are dependent on patterned neuronal activity. It has been assumed that changes in neuronal excitability underlie processes of neural repair and remapping of cortical sensory and motor representations. Indeed, recent evidence suggests that local inhibitory and excitatory currents are altered after stroke and modulation of these networks to enhance excitability during the repair phase can facilitate functional recovery after stroke. More specifically, dampening tonic GABA inhibition can afford an early and robust improvement in functional recovery after stroke.
Both exogenous and endogenous cannabinoids can allosterically modulate glycine receptors (GlyRs). However, little is known about the molecular basis of cannabinoid-GlyR interactions. Here we report that sustained incubation with the endocannabinoid anandamide (AEA) substantially increased the amplitude of glycine-activated current in both rat cultured spinal neurons and in HEK-293 cells expressing human α1, rat α2 and α3 GlyRs. While the α1 and α3 subunits were highly sensitive to AEA-induced potentiation, the α2 subunit was relatively insensitive to AEA. Switching a serine at 296 and 307 in the TM3 (transmembrane domain 3) of the α1 and α3 subunits with an alanine (A) at the equivalent position in the α2 subunit converted the α1/α3 AEA-sensitive receptors to sensitivity resembling that of α2. The S296 residue is also critical for exogenous cannabinoid-induced potentiation of I(Gly). The magnitude of AEA potentiation decreased with removal of either the hydroxyl or oxygen groups on AEA. While desoxy-AEA was significantly less efficacious in potentiating I(Gly), desoxy-AEA inhibited potentiation produced by both Δ(9)-tetrahydrocannabinol (THC), a major psychoactive component of marijuana, and AEA. Similarly, didesoxy-THC, a modified THC with removal of both hydroxyl/oxygen groups, did not affect I(Gly) when applied alone but inhibited the potentiation of I(Gly) induced by AEA and THC. These findings suggest that exogenous and endogenous cannabinoids potentiate GlyRs via a hydrogen bonding-like interaction. Such a specific interaction likely stems from a common molecular basis involving the S296 residue in the TM3 of the α1 and α3 subunits.
The potency of GABA is vitally important for its primary role in activating GABA(A) receptors and acting as an inhibitory neurotransmitter. Although numerous laboratories have presented information, directly or indirectly, on GABA potency, it is often difficult to compare across such studies given the inevitable variations in the methods used, the cell types studied, whether native or recombinant receptors are examined, and their relevance to native synaptic and extrasynaptic GABA(A) receptors. In this review, we list the most relevant isoforms of synaptic and extrasynaptic GABA(A) receptors that are thought to assemble in surface membranes of neurons in the central nervous system. Using consistent methodology in one cell type, the potencies of the endogenous neurotransmitter GABA are compared across a spectrum of GABA(A) receptors. The highest potency for GABA is measured when activating extrasynaptic-type α6 subunit-containing receptors, whereas synaptic-type α2β3γ2 and α3β3γ2 receptors exhibited the lowest potency, and other GABA(A) receptor subtypes that are found both in synaptic and extrasynaptic compartments, showed intermediate sensitivities to GABA. The relatively simple potency relationship between GABA and its target receptors is important as it serves as one of the major determinants of GABA(A) receptor activation, with consequences for the development of inhibition, either by tonic or phasic mechanisms.
GABA(A) receptors are the major ionotropic inhibitory neurotransmitter receptors. The endocannabinoid system is a lipid signaling network that modulates different brain functions. Here we show a direct molecular interaction between the two systems. The endocannabinoid 2-arachidonoyl glycerol (2-AG) potentiates GABA(A) receptors at low concentrations of GABA. Two residues of the receptor located in the transmembrane segment M4 of β(2) confer 2-AG binding. 2-AG acts in a superadditive fashion with the neurosteroid 3α, 21-dihydroxy-5α-pregnan-20-one (THDOC) and modulates δ-subunit-containing receptors, known to be located extrasynaptically and to respond to neurosteroids. 2-AG inhibits motility in CB(1)/CB(2) cannabinoid receptor double-KO, whereas β(2)-KO mice show hypermotility. The identification of a functional binding site for 2-AG in the GABA(A) receptor may have far-reaching consequences for the study of locomotion and sedation.
Glycine receptors (GlyRs) are transmitter-gated anion channels of the Cys-loop superfamily which mediate synaptic inhibition at spinal and selected supraspinal sites. Although they serve pivotal functions in motor control and sensory processing, they have yet to be exploited as drug targets partly because of hitherto limited possibilities for allosteric control. Endocannabinoids (ECs) have recently been characterized as direct allosteric GlyR modulators, but the underlying molecular sites have remained unknown. Here, we show that chemically neutral ECs (e.g. anandamide, AEA) are positive modulators of α(1), α(2) and α(3) GlyRs, whereas acidic ECs (e.g. N-arachidonoyl-glycine; NA-Gly) potentiate α(1) GlyRs but inhibit α(2) and α(3). This subunit-specificity allowed us to identify the underlying molecular sites through analysis of chimeric and mutant receptors. We found that alanine 52 in extracellular loop 2, glycine 254 in transmembrane (TM) region 2 and intracellular lysine 385 determine the positive modulation of α(1) GlyRs by NA-Gly. Successive substitution of non-conserved extracellular and TM residues in α(2) converted NA-Gly-mediated inhibition into potentiation. Conversely, mutation of the conserved lysine within the intracellular loop between TM3 and TM4 attenuated NA-Gly-mediated potentiation of α(1) GlyRs, without affecting inhibition of α(2) and α(3). Notably, this mutation reduced modulation by AEA of all three GlyRs. These results define molecular sites for allosteric control of GlyRs by ECs and reveal an unrecognized function for the TM3-4 intracellular loop in the allosteric modulation of Cys-loop ion channels. The identification of these sites may help to understand the physiological role of this modulation and facilitate the development of novel therapeutic approaches to diseases such as spasticity, startle disease and possibly chronic pain.
Phytocannabinoids are useful therapeutics for multiple applications including treatments of constipation, malaria, rheumatism, alleviation of intraocular pressure, emesis, anxiety and some neurological and neurodegenerative disorders. Consistent with these medicinal properties, extracted cannabinoids have recently gained much interest in research, and some are currently in advanced stages of clinical testing. Other constituents of Cannabis sativa, the hemp plant, however, remain relatively unexplored in vivo. These include cannabidiol (CBD), cannabidivarine (CBDV), Δ(9)-tetrahydrocannabivarin (Δ(9)-THCV) and cannabigerol (CBG).
We here determined pharmacokinetic profiles of the above phytocannabinoids after acute single-dose intraperitoneal and oral administration in mice and rats. The pharmacodynamic-pharmacokinetic relationship of CBD (120 mg/kg, ip and oral) was further assessed using a marble burying test in mice.
All phytocannabinoids readily penetrated the blood-brain barrier and solutol, despite producing moderate behavioural anomalies, led to higher brain penetration than cremophor after oral, but not intraperitoneal exposure. In mice, cremophor-based intraperitoneal administration always attained higher plasma and brain concentrations, independent of substance given. In rats, oral administration offered higher brain concentrations for CBD (120 mg/kg) and CBDV (60 mg/kg), but not for Δ(9)-THCV (30 mg/kg) and CBG (120 mg/kg), for which the intraperitoneal route was more effective. CBD inhibited obsessive-compulsive behaviour in a time-dependent manner matching its pharmacokinetic profile.
These data provide important information on the brain and plasma exposure of new phytocannabinoids and guidance for the most efficacious administration route and time points for determination of drug effects under in vivo conditions.
Mutations in brain isoforms of voltage-gated sodium channels have been identified in patients with distinct epileptic phenotypes. Clinically, these patients often do not respond well to classic anti-epileptics and many remain refractory to treatment. Exogenous as well as endogenous cannabinoids have been shown to target voltage-gated sodium channels and cannabidiol has recently received attention for its potential efficacy in the treatment of childhood epilepsies. In this study, we further investigated the ability of cannabinoids to modulate sodium currents from wild-type and epilepsy-associated mutant voltage-gated sodium channels. We first determined the biophysical consequences of epilepsy-associated missense mutations in both Nav1.1 (arginine 1648 to histidine and asparagine 1788 to lysine) and Nav1.6 (asparagine 1768 to aspartic acid and leucine 1331 to valine) by obtaining whole-cell patch clamp recordings in human embryonic kidney 293T cells with 200 μM Navβ4 peptide in the pipette solution to induce resurgent sodium currents. Resurgent sodium current is an atypical near threshold current predicted to increase neuronal excitability and has been implicated in multiple disorders of excitability. We found that both mutations in Nav1.6 dramatically increased resurgent currents while mutations in Nav1.1 did not. We then examined the effects of anandamide and cannabidiol on peak transient and resurgent currents from wild-type and mutant channels. Interestingly, we found that cannabidiol can preferentially target resurgent sodium currents over peak transient currents generated by wild-type Nav1.6 as well as the aberrant resurgent and persistent current generated by Nav1.6 mutant channels. To further validate our findings, we examined the effects of cannabidiol on endogenous sodium currents from striatal neurons, and similarly we found an inhibition of resurgent and persistent current by cannabidiol. Moreover, current clamp recordings show that cannabidiol reduces overall action potential firing of striatal neurons. These findings suggest that cannabidiol could be exerting its anticonvulsant effects, at least in part, through its actions on voltage-gated sodium channels, and resurgent current may be a promising therapeutic target for the treatment of epilepsy syndromes.
Extrasynaptically located γ-aminobutyric acid (GABA) receptors type A are often characterized by the presence of a δ subunit in the receptor complex. δ-Containing receptors respond to low ambient concentrations of GABA, or respond to spillover of GABA from the synapse, and give rise to tonic inhibitory currents. In certain brain regions, e.g. thalamocortical neurons, tonic inhibition is estimated to represent the majority of total GABA-mediated inhibition, which has raised substantial interest in extrasynaptic receptors as potential drug targets. Thalamocortical neurons typically express α4β2/3δ receptors, however, these have proven difficult to study in recombinant in vitro expression systems due to the inherently low current levels elicited in response to GABA.
In this study, we sought to characterize a range of agonists and positive allosteric modulators at α4β2δ and α4β2γ2 receptors. All tested agonists (GABA, THIP, muscimol, and taurine) displayed between 8 and 22 fold increase in potency at the α4β2δ receptor. In contrast, modulatory potencies of steroids (allopregnanolone, THDOC and alfaxalone), anesthetics (etomidate, pentobarbital) and Delta-Selective agents 1 and 2 (DS1 and DS2) were similar at α4β2δ and α4β2γ2 receptors. When evaluating modulatory efficacies, the neurosteroids and anesthetics displayed highest efficacy at α4β2γ2 receptors whereas DS1 and in particular DS2 had highest efficacy at α4β2δ receptors. Overall, several key messages emerged: (i) none of the tested compounds displayed significant selectivity and a great need for identifying new δ-selective compounds remains; (ii) α4β2δ and α4β2γ2 receptors have such divergent intrinsic activation properties that valid comparisons of modulator efficacies are at best challenging.
The 5-HT3 and glycine receptors are pentameric ion channels belonging to a Cys-loop ligand-gated ion channel superfamily. While the glycine receptors can mediate fast inhibitory synaptic transmission, the 5-HT3 receptors are involved in both excitatory and inhibitory synaptic transmission in the central and peripheral nervous system. These receptors play important roles in several physiological and pathological processes such as vomiting reflex, neuromotor activity, pain process, reward mechanism of drugs of abuse, cognition, and anxiety control. Emerging evidence has identified both receptors as primary targets for the action of nonpsychoactive cannabinoids in the brain. Psychoactive and nonpsychoactive cannabinoids alter the amplitudes of 5-hydroxytryptamine and glycine-activated currents in native neurons and in cell lines expressing recombinant 5-HT3 and glycine receptors through CB1 and CB2 receptor-independent mechanisms. However, little is known about molecular mechanisms and behavioral implications of this specific cannabinoid modulation. Results from recent studies have shed light on the molecular basis of nonpsychoactive cannabinoid modulation of glycine receptors. Evidence has also emerged to suggest that cannabinoid modulation of glycine receptors contributes to some of the cannabis-induced analgesic effect. This research direction could help develop novel therapeutic agents for the treatment of pain and other diseases. This chapter summarizes recent research progress in our knowledge about the mechanisms and in vivo consequence of cannabinoid modulation of 5-HT3 and glycine receptors.
GABAA receptors that contain the α4 and δ subunits are thought to be located extrasynaptically, mediating tonic currents elicited by low concentrations of GABA. These α4βδ receptors are modulated by neurosteroids and certain anesthetics, identifying them as important drug targets in research. However, pharmacological studies on these receptors have often yielded variable results, possibly due to the expression of receptors in different stoichiometries or arrangements.
In this study, we injected different ratios of α4, β2 and δ cRNA into Xenopus oocytes and measured the sensitivity to GABA and DS2 activation of the resulting receptor populations. By creating a matrix of RNA injection ratios from stock RNA concentrations, we were able to compare the changes in pharmacology between injection ratios where the ratio of only one subunit was altered.
We identified two distinct populations of receptors, the first with an EC50 value of approximately 100 nM to GABA, a low Hill slope of approximately 0.3 and substantial direct activation by DS2. The second population had an EC50 value of approximately 1 μM to GABA, a steeper Hill slope of 1 and little direct activation, but substantial potentiation, by DS2. The second population was formed with high α4 ratios and low β2 ratios, but altering the ratio of δ subunit injected had little effect. We propose that receptors with high sensitivity to GABA and direct activation by DS2 are the result of a greater number of β2 subunits being incorporated into the receptor.
Background:
Almost a third of patients with epilepsy have a treatment-resistant form, which is associated with severe morbidity and increased mortality. Cannabis-based treatments for epilepsy have generated much interest, but scientific data are scarce. We aimed to establish whether addition of cannabidiol to existing anti-epileptic regimens would be safe, tolerated, and efficacious in children and young adults with treatment-resistant epilepsy.
Methods:
In this open-label trial, patients (aged 1-30 years) with severe, intractable, childhood-onset, treatment-resistant epilepsy, who were receiving stable doses of antiepileptic drugs before study entry, were enrolled in an expanded-access programme at 11 epilepsy centres across the USA. Patients were given oral cannabidiol at 2-5 mg/kg per day, up-titrated until intolerance or to a maximum dose of 25 mg/kg or 50 mg/kg per day (dependent on study site). The primary objective was to establish the safety and tolerability of cannabidiol and the primary efficacy endpoint was median percentage change in the mean monthly frequency of motor seizures at 12 weeks. The efficacy analysis was by modified intention to treat. Comparisons of the percentage change in frequency of motor seizures were done with a Mann-Whitney U test.
Results:
Between Jan 15, 2014, and Jan 15, 2015, 214 patients were enrolled; 162 (76%) patients who had at least 12 weeks of follow-up after the first dose of cannabidiol were included in the safety and tolerability analysis, and 137 (64%) patients were included in the efficacy analysis. In the safety group, 33 (20%) patients had Dravet syndrome and 31 (19%) patients had Lennox-Gastaut syndrome. The remaining patients had intractable epilepsies of different causes and type. Adverse events were reported in 128 (79%) of the 162 patients within the safety group. Adverse events reported in more than 10% of patients were somnolence (n=41 [25%]), decreased appetite (n=31 [19%]), diarrhoea (n=31 [19%]), fatigue (n=21 [13%]), and convulsion (n=18 [11%]). Five (3%) patients discontinued treatment because of an adverse event. Serious adverse events were reported in 48 (30%) patients, including one death-a sudden unexpected death in epilepsy regarded as unrelated to study drug. 20 (12%) patients had severe adverse events possibly related to cannabidiol use, the most common of which was status epilepticus (n=9 [6%]). The median monthly frequency of motor seizures was 30·0 (IQR 11·0-96·0) at baseline and 15·8 (5·6-57·6) over the 12 week treatment period. The median reduction in monthly motor seizures was 36·5% (IQR 0-64·7).
Interpretation:
Our findings suggest that cannabidiol might reduce seizure frequency and might have an adequate safety profile in children and young adults with highly treatment-resistant epilepsy. Randomised controlled trials are warranted to characterise the safety profile and true efficacy of this compound.
Funding:
GW Pharmaceuticals, Epilepsy Therapy Project of the Epilepsy Foundation, Finding A Cure for Epilepsy and Seizures.
Background and purpose:
It has been proposed that medicinal strains of cannabis and therapeutic preparations would be safer with a more balanced concentration ratio of Δ9-tetrahydrocannabinol (THC) to cannabidiol (CBD), as CBD reduces the adverse psychotropic effects of THC. However, our understanding of CBD and THC interactions is limited and the brain circuitry mediating interactions between CBD and THC are unknown. The aim of this study is to investigate whether CBD modulates THC-induced functional effects and c-Fos expression in a 1:1 dose ratio that approximates therapeutic strains of cannabis and nabiximols.
Experimental approach:
Male C57BL/6 mice were treated with vehicle, CBD, THC, or a combination of CBD and THC (10 mg.kg(-1) i.p. for both cannabinoids) to examine effects on locomotor activity, anxiety-related behaviour, body temperature, and brain c-Fos expression (a marker of neuronal activation).
Key results:
CBD potentiated THC-induced locomotor suppression but reduced the hypothermic and anxiogenic effects of THC. CBD alone had no effect on these measures. THC increased brain activation as measured by c-Fos expression in 11 of the 35 brain regions studied; CBD co-administration suppressed THC-induced c-Fos expression in 6 of these brains regions. This effect was most pronounced in the medial preoptic nucleus and lateral PAG. CBD alone treatment diminished c-Fos expression only in the central nucleus of the amygdala compared to vehicle.
Conclusions and implications:
These data re-affirm that CBD modulates the pharmacological actions of THC and provide information regarding brain regions involved in the interaction between CBD and THC.
Cannabidiol has been reported to act as an antagonist of cannabinoid agonists at type 1 cannabinoid receptors (CB1 ). We hypothesized that cannabidiol can inhibit cannabinoid agonist activity through negative allosteric modulation of CB1 .
CB1 internalization, arrestin2 recruitment, and PLCβ3 and ERK1/2 phosphorylation, were quantified in HEK 293A cells heterologously expressing CB1 and in the STHdh(Q7/Q7) cell model of striatal neurons endogenously expressing CB1 . Cells were treated with 2-arachidonylglycerol or Δ(9) -tetrahydrocannabinol alone and in combination with different concentrations of cannabidiol.
Cannabidiol reduced the efficacy and potency of 2-arachidonylglycerol and Δ(9) -tetrahydrocannabinol on PLCβ3- and ERK1/2-dependent signaling in cells heterologously (HEK 293A) or endogenously (STHdh(Q7/Q7) ) expressing CB1 . By reducing arrestin2 recruitment to CB1 , cannabidiol treatment prevented CB1 internalization. The allosteric activity of cannabidiol depended upon polar residues being present at positions 98 and 107 in the extracellular amino-terminus.
Cannabidiol behaved as a non-competitive negative allosteric modulator of CB1 . Allosteric modulation, in conjunction with non-CB1 effects, may explain the in vivo effects of cannabidiol. Allosteric modulators of CB1 have the potential to treat central nervous system and peripheral disorders while avoiding the adverse effects associated with orthosteric agonism or antagonism of CB1 . This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Under an expanded access investigational new drug (IND) trial, cannabidiol (CBD) is being studied as a possible adjuvant treatment of refractory epilepsy in children. Of the 25 subjects in the trial, 13 were being treated with clobazam (CLB). Because CLB and CBD are both metabolized in the cytochrome P450 (CYP) pathway, we predicted a drug-drug interaction, which we evaluate in this article.
Thirteen subjects with refractory epilepsy concomitantly taking CLB and CBD under IND 119876 were included in this study. Demographic information was collected for each subject including age, sex, and etiology of seizures, as well as concomitant antiepileptic drugs (AEDs). CLB, N-desmethylclobazam (norclobazam; nCLB), and CBD levels were measured over the course of CBD treatment. CLB doses were recorded at baseline and at weeks 4 and 8 of CBD treatment. Side effects were monitored.
We report elevated CLB and nCLB levels in these subjects. The mean (± standard deviation [SD]) increase in CLB levels was 60 ± 80% (95% confidence interval (CI) [-2-91%] at 4 weeks); the mean increase in nCLB levels was 500 ± 300% (95% CI [+90-610%] at 4 weeks). Nine of 13 subjects had a >50% decrease in seizures, corresponding to a responder rate of 70%. The increased CLB and nCLB levels and decreases in seizure frequency occurred even though, over the course of CBD treatment, CLB doses were reduced for 10 (77%) of the 13 subjects. Side effects were reported in 10 (77%) of the 13 subjects, but were alleviated with CLB dose reduction.
Monitoring of CLB and nCLB levels is necessary for clinical care of patients concomitantly on CLB and CBD. Nonetheless, CBD is a safe and effective treatment of refractory epilepsy in patients receiving CLB treatment.
Wiley Periodicals, Inc. © 2015 International League Against Epilepsy.
There is a great need for safe and effective therapies for treatment of infantile spasms (IS) and Lennox-Gastaut syndrome (LGS). Based on anecdotal reports and limited experience in an open-label trial, cannabidiol (CBD) has received tremendous attention as a potential treatment for pediatric epilepsy, especially Dravet syndrome. However, there is scant evidence of specific utility for treatment of IS and LGS. We sought to document the experiences of children with IS and/or LGS who have been treated with CBD-enriched cannabis preparations. We conducted a brief online survey of parents who administered CBD-enriched cannabis preparations for the treatment of their children's epilepsy. We specifically recruited parents of children with IS and LGS and focused on perceived efficacy, dosage, and tolerability. Survey respondents included 117 parents of children with epilepsy (including 53 with IS or LGS) who had administered CBD products to their children. Perceived efficacy and tolerability were similar across etiologic subgroups. Eighty-five percent of all parents reported a reduction in seizure frequency, and 14% reported complete seizure freedom. Epilepsy was characterized as highly refractory with median latency from epilepsy onset to CBD initiation of five years, during which the patient's seizures failed to improve after a median of eight antiseizure medication trials. The median duration and the median dosage of CBD exposure were 6.8months and 4.3mg/kg/day, respectively. Reported side effects were far less common during CBD exposure, with the exception of increased appetite (30%). A high proportion of respondents reported improvement in sleep (53%), alertness (71%), and mood (63%) during CBD therapy. Although this study suggests a potential role for CBD in the treatment of refractory childhood epilepsy including IS and LGS, it does not represent compelling evidence of efficacy or safety. From a methodological standpoint, this study is extraordinarily vulnerable to participation bias and limited by lack of blinded outcome ascertainment. Appropriately controlled clinical trials are essential to establish efficacy and safety.
Copyright © 2015 Elsevier Inc. All rights reserved.