Article

An acute dose-ranging evaluation of the antidepressant properties of Sceletium tortuosum (Zembrin®) versus escitalopram in the Flinders Sensitive Line rat

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Abstract

Ethnopharmacological relevance Sceletium tortuosum (L.) N.E.Br. (ST) has been used by the Khoisan people of South Africa as a mood elevator. Its various pharmacological mechanisms of action suggest distinct potential as an antidepressant. Clinical studies in healthy individuals suggest beneficial effects on mood, cognition, and anxiety. Aim of the study To obtain a chromatographic fingerprint of a standardized extract of S. tortuosum (Zembrin®), and to evaluate the acute antidepressant-like properties of Zembrin® versus the reference antidepressant, escitalopram, in the Flinders Sensitive Line (FSL) rat, a genetic rodent model of depression. Materials and methods The chemical profile of Zembrin® was determined by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) chromatogram method using alkaloid standards. Twelve saline treated FSL and six Flinders Resistant Line (FRL) control rats were used to confirm face validity of the FSL model using the forced swim test (FST). Thereafter, FSL rats (n = 10) received either 5, 10, 25, 50 or 100 mg/kg of Zembrin®, or 5, 10 or 20 mg/kg escitalopram oxalate (ESC), both via oral gavage, and subjected to the open field test (OFT) and FST. Results Four main ST alkaloids were identified and quantified in Zembrin® viz. mesembrenone, mesembrenol, mesembrine, and mesembranol (47.9%, 32%, 13.2%, and 6.8% of the total alkaloids, respectively). FSL rats showed significantly decreased swimming and climbing (coping) behaviours, and significantly increased immobility (despair), versus FRL controls. ESC 5 mg/kg and Zembrin® 25 mg/kg and 50 mg/kg showed significant dose-dependent reversal of immobility in FSL rats and variable effects on coping behaviours. Zembrin® 50 mg/kg was the most effective antidepressant dose, showing equivalence to ESC 5. Conclusions Zembrin® (25 and 50 mg/kg) and ESC (5 mg/kg) are effective antidepressants after acute treatment in the FST. Moreover, Zembrin® 50 mg/kg proved equivalent to ESC 5. Further long-term bio-behavioural studies on the antidepressant properties of Zembrin® are warranted.

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... In a more recent acute dose-ranging study in rats, varying doses of a standardized extract of Sceletium, Zembrin®, viz. 5, 10, 25, 50 or 100 mg/kg, were evaluated with respect to anti-depressant-like properties in a genetic rodent model of depression, the Flinders Sensitive Line (FSL) rat (Gericke et al., 2021). This dosage range was selected to coincide with the clinical literature described below. ...
... In a more recent acute dose-ranging study in rats, varying doses of a standardized extract of Sceletium, Zembrin®, viz. 5, 10, 25, 50 or 100 mg/kg, were evaluated with respect to anti-depressant-like properties in a genetic rodent model of depression, the Flinders Sensitive Line (FSL) rat (Gericke et al., 2021). This dosage range was selected to coincide with the clinical literature described below. ...
Article
Ethnopharmacological relevance Sceletium tortuosum (L.) N.E.Br., the most sought after and widely researched species in the genus Sceletium is a succulent forb endemic to South Africa. Traditionally, this medicinal plant is mainly masticated or smoked and used for the relief of toothache, abdominal pain, as a mood-elevator, analgesic, hypnotic, anxiolytic, thirst and hunger suppressant, and for its intoxicating/euphoric effects. Sceletium tortuosum is currently of widespread scientific interest due to its clinical potential in treating anxiety and depression, relieving stress in healthy individuals, and enhancing cognitive functions. These pharmacological actions are attributed to its phytochemical constituents referred to as mesembrine-type alkaloids. Aim of the review The aim of this review was to comprehensively summarize and critically evaluate recent research advances on the phytochemistry, pharmacokinetics, biological, pre-clinical and clinical activities of the medicinal plant S. tortuosum. Additionally, current ongoing research and future perspectives are also discussed. Methods All relevant scientific articles, books, MSc and Ph.D. dissertations on botany, behavioral pharmacology, traditional uses, and phytochemistry of S. tortuosum were retrieved from different databases (including Science Direct, PubMed, Google Scholar, Scopus and Web of Science). For pharmacokinetics and pharmacological effects of S. tortuosum, the focus fell on relevant publications published between 2009 and 2021. Results Twenty-five alkaloids belonging to four structural classes viz: mesembrine, Sceletium A4, joubertiamine, and tortuosamine, have been identified from S. tortuosum, of which the mesembrine class is predominant. The crude extracts and commercially available standardized extracts of S. tortuosum have displayed a wide spectrum of biological activities (e.g. antimalarial, anti-oxidant, neuromodulatory, immunomodulatory, anti-HIV, neuroprotection) in in vitro or in vivo studies. While the plant has been studied in clinical populations, this has only been in healthy subjects, so that further study in pathological states remains to be done. Nevertheless, the aforementioned studies have demonstrated that S. tortuosum has potential for enhancing cognitive function and managing anxiety and depression. Conclusion As an important South African medicinal plant, S. tortuosum has garnered many research advances on its phytochemistry and biological activities over the last decade. These scientific studies have shown that S. tortuosum has various bioactivities. The findings have further established the link between the phytochemistry and pharmacological application, and support the traditional use of S. tortuosum in the indigenous medicine of South Africa.
... In a more recent acute dose-ranging study in rats, varying doses of a standardized extract of Sceletium, Zembrin®, viz. 5, 10, 25, 50 or 100 mg/kg, were evaluated with respect to anti-depressant-like properties in a genetic rodent model of depression, the Flinders Sensitive Line (FSL) rat (Gericke et al., 2021). This dosage range was selected to coincide with the clinical literature described below. ...
Article
Ethnopharmacological relevance Sceletium tortuosum (L.) N.E.Br, the most sought after and widely researched species in the genus Sceletium is a succulent forb endemic to South Africa. Traditionally, this medicinal plant is mainly masticated or smoked and used for the relief of toothache, abdominal pain, and as a mood-elevator, analgesic, hypnotic, anxiolytic, thirst and hunger suppressant, and for its intoxicating/euphoric effects. Sceletium tortuosum is currently of widespread scientific interest due to its clinical potential in treating anxiety and depression, relieving stress in healthy individuals, and enhancing cognitive functions. These pharmacological actions are attributed to its phytochemical constituents referred to as mesembrine-type alkaloids. Aim of the review The aim of this review was to comprehensively summarize and critically evaluate recent research advances on the phytochemistry, pharmacokinetics, biological and clinical activities of the medicinal plant S. tortuosum. Additionally, current ongoing research and future perspectives are also discussed. Methods All relevant scientific articles, books, MSc and Ph.D. dissertations on botany, behavioral pharmacology, traditional uses, and phytochemistry of S. tortuosum were retrieved from different databases (including Science Direct, PubMed, Google Scholar, Scopus and Web of Science). For pharmacokinetics and pharmacological effects of S. tortuosum, the focus fell on relevant publications published between 2009 and 2021. Results Twenty-five alkaloids belonging to four structural classes viz: mesembrine, Sceletium A4, joubertiamine, and tortuosamine, have been identified from S. tortuosum, of which the mesembrine class is predominant. The crude extracts and commercially available standardized extracts of S. tortuosum have displayed a wide spectrum of biological activities (e.g. antimalarial, anti-oxidant, immunomodulatory, anti-HIV, neuroprotection, enhancement of cognitive function) in in vitro or in vivo studies. This plant has not yet been studied in a clinical population, but has potential for enhancing cognitive function, and managing anxiety and depression. Conclusion As an important South African medicinal plant, S. tortuosum has garnered many research advances on its phytochemistry and biological activities over the last decade. These scientific studies have shown that S. tortuosum has various bioactivities. The findings have further established the link between the phytochemistry and pharmacological application, and support the traditional use of S. tortuosum in the indigenous medicine of South Africa.
Article
Depression is the most prevalent and devastating neuropsychiatric disorder. There are several conventional antidepressants used for the treatment of depression. But due to their undesired adverse effects, patient compliance is very poor. Thus, developing novel medications for the treatment of depression is a critical strategic priority for meeting therapeutic demands. Current research is looking for alternatives to traditional antidepressants to reduce undesired side effects and increase efficacy. Phytoconstituents provide a wide research range in antidepressant treatments. In the present article, we have conducted a comprehensive assessment of neurological evidence, which supports the usefulness of phytoconstituents in the treatment of the depressive disorder. Secondary plant metabolites including alkaloids, polyphenols, glycosides, saponins, and terpenoids were found to exhibit antidepressant action. Most of the phytoconstituents were found to mediate their antidepressant effect through the upregulation of brain-derived neurotrophic factor (BDNF), serotonin, noradrenaline, and dopamine. Some were also found to exert antidepressant effects by inhibiting the monoamine oxidase (MAO) activity and hypothalamic-pituitary-adrenal (HPA) axis overactivity.
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A well-characterized standardized hydroethanolic extract of a traditionally recognized mak (mild) variety of Sceletium tortuosum, a South African plant with a long history of traditional ingestion, is marketed under the trade name Zembrin® as an ingredient for use in functional foods and dietary supplements. It is standardized to contain 0.35–0.45% total alkaloids (mesembrenone and mesembrenol ≥60%, and mesembrine <20%). A 14-day repeated oral toxicity study was conducted at 0, 250, 750, 2500, and 5000 mg/kg bw/d. A 90-day subchronic repeated oral toxicity study was conducted at 0, 100, 300, 450, and 600 mg/kg bw/d. Because S. tortuosum has a long history of human use for relieving stress and calming, a functional observation battery, including spontaneous locomotor activity measured using LabMaster ActiMot light-beam frames system, was employed. Several parameters, such as locomotion, rearing behavior, spatial parameters, and turning behavior were investigated in the final week of the study. No mortality or treatment-related adverse effects were observed in male or female Crl:(WI)BR Wistar rats in the 14- or 90-day studies. In the 14- and 90-day studies, the NOAELs were concluded as 5000 and 600 mg/kg bw/d, respectively, the highest dose groups tested.
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Depression may relate to neurocognitive impairment that results from alteration of N-methyl-D: -aspartate receptor (NMDAR) levels. Venlafaxine and escitalopram are two drugs commonly used to treat depression. The drugs may affect expression of NMDARs, which mediate learning and memory formation. The aim of the study was to examine whether the effects of venlafaxine and escitalopram treatments are associated with NMDARs in a rat model of depression. Forty male Wistar albino rats were randomly divided into four groups (n = 10) as follows: control group, chronic mild stress group (CMS), venlafaxine (20 mg/kg body weight per day) + CMS, and escitalopram (10 mg/kg body weight per day) + CMS. After induction of depression, a decrease in the concentration of NR2B was observed; venlafaxine treatment prevented the reduction of NR2B expression. Escitalopram treatment did not effect the reduced levels of NR2B resulting from depression. There was no significant difference in NR2A concentration among groups. The present data support the notion that venlafaxine plays a role in maintaining NR2B receptor in experimental depression. It may be possible that treatment with escitalopram has no effect on NMDARs in experimental depression.
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We investigated the effects of lamotrigine, aripiprazole and escitalopram administration and experimental depression on lipid peroxidation (LP) and antioxidant levels in cortex of the brain in rats. Forty male wistar rats were randomly divided into five groups. First group was used as control although second group was depression-induced group. Aripiprazole, lamotrigine and escitalopram per day were orally supplemented to chronic mild stress (CMS) depression-induced rats constituting the third, fourth and fifth groups for 28 days, respectively. Depression resulted in significant decrease in the glutathione peroxidase (GSH-Px) activity, reduced glutathione and vitamin C of cortex of the brain although their levels and beta-carotene concentrations were increased by the three drugs administrations to the animals of CMS induced depression group. The LP levels in the cortex of the brain and plasma of depression group were elevated although their levels were decreased by the administrations. The increases of antioxidant values in lamotrigine group were higher according to aripiprazole and escitalopram supplemented groups. Vitamin A level did not change in the five groups. In conclusion, the experimental depression is associated with elevated oxidative stress although treatment with lamotrigine has most protective effects on the oxidative stress within three medicines.
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Ethnopharmacological relevance Sceletium tortuosum (L.) N.E.Br, the most sought after and widely researched species in the genus Sceletium is a succulent forb endemic to South Africa. Traditionally, this medicinal plant is mainly masticated or smoked and used for the relief of toothache, abdominal pain, and as a mood-elevator, analgesic, hypnotic, anxiolytic, thirst and hunger suppressant, and for its intoxicating/euphoric effects. Sceletium tortuosum is currently of widespread scientific interest due to its clinical potential in treating anxiety and depression, relieving stress in healthy individuals, and enhancing cognitive functions. These pharmacological actions are attributed to its phytochemical constituents referred to as mesembrine-type alkaloids. Aim of the review The aim of this review was to comprehensively summarize and critically evaluate recent research advances on the phytochemistry, pharmacokinetics, biological and clinical activities of the medicinal plant S. tortuosum. Additionally, current ongoing research and future perspectives are also discussed. Methods All relevant scientific articles, books, MSc and Ph.D. dissertations on botany, behavioral pharmacology, traditional uses, and phytochemistry of S. tortuosum were retrieved from different databases (including Science Direct, PubMed, Google Scholar, Scopus and Web of Science). For pharmacokinetics and pharmacological effects of S. tortuosum, the focus fell on relevant publications published between 2009 and 2021. Results Twenty-five alkaloids belonging to four structural classes viz: mesembrine, Sceletium A4, joubertiamine, and tortuosamine, have been identified from S. tortuosum, of which the mesembrine class is predominant. The crude extracts and commercially available standardized extracts of S. tortuosum have displayed a wide spectrum of biological activities (e.g. antimalarial, anti-oxidant, immunomodulatory, anti-HIV, neuroprotection, enhancement of cognitive function) in in vitro or in vivo studies. This plant has not yet been studied in a clinical population, but has potential for enhancing cognitive function, and managing anxiety and depression. Conclusion As an important South African medicinal plant, S. tortuosum has garnered many research advances on its phytochemistry and biological activities over the last decade. These scientific studies have shown that S. tortuosum has various bioactivities. The findings have further established the link between the phytochemistry and pharmacological application, and support the traditional use of S. tortuosum in the indigenous medicine of South Africa.
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Modern-day regulatory systems governing conditions for how health products enter national markets constitute a barrier of access for traditional herbal medicines on an international level. Regulatory intentions are focused on ensuring consumers are being provided with safe, efficacious and high-quality products that, however, collaterally limit opportunities for traditional herbal medicinal products, especially those that do not already have a long-standing tradition of use established in the respective national marketplaces. This case study investigates and compares how a Southern African herbal medicine with great potential as an anxiolytic and mild antidepressant – Mesembryanthemum tortuosum L. [syn. Sceletium tortuosum (L.) N.E.Br.] aerial parts – fares internationally in today’s regulatory environments. It is argued that inadvertent regulatory favoritism combined with the lack of means for adequate protection of intellectual property may obstruct innovation by creating an almost insurmountable economical hurdle for successful product development and introduction of botanicals from developing countries into most of the world’s health product markets.
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Non-selective α2-adrenoreceptor (AR) stimulation delivers favourable sedative, analgesic, muscle relaxant and anxiolytic actions in companion animals, but is associated with cardiovascular and respiratory side effects. Anxiety conditions underscore monoamine disturbances amenable to α2-AR modulation. We investigated sub-chronic (14 day s.c.) treatment with the selective α2C-AR antagonist, ORM-10921 (0.03, 0.1, 0.3 mg/kg/d) on hippocampal noradrenaline (NA), dopamine (DA), serotonin (5-HT) and their turnover levels in stress sensitive Flinders Sensitive Line (FSL) rats versus Flinders Resistant Line (FRL) controls, using high performance liquid chromatography. The effects of ORM-10921 were compared to the non-selective α2-AR antagonist, idazoxan (IDAZ; 3 mg/kg/d), and to imipramine (IMI; 15 mg/kg/d), a reference antidepressant in this model. FSL rats displayed significantly reduced 5-HT (p = 0.03) and DA (p = 0.02) levels vs. FRL controls, while NA levels showed a similar trend. ORM-10921 significantly increased NA (all doses p ≤ 0.02), 5-HT (0.1 and 0.3 mg/kg p ≤ 0.03) and DA levels (all doses p ≤ 0.03), which correlated with decreased monoamine turnover. In contrast, IDAZ significantly elevated NA (p < 0.005) and DA (p < 0.004) but not 5-HT levels. IMI also significantly increased 5-HT (p < 0.009), with a tendency to increase NA (p = 0.09) but not DA. ORM-10921 exerts similar albeit broader effects on hippocampal monoamines than IDAZ, explaining earlier established efficacy associated with α2C-AR antagonism in animal models of depression and cognitive dysfunction. These and the current studies encourage application of ORM-10921 in depression in humans, as well as raise the intriguing possibility that selective α2C-AR antagonists may be beneficial in anxiety and stress-related disorders in companion animals. Both warrant further study.
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The usage of traditional Chinese medicines has expanded globally, but the data about authentication, efficacy, and safety is far from sufficient to meet the criteria supporting their use worldwide due to complexity in the composition. Fingerprinting describes integral characterization and reflects interactive aspects of complex components; therefore, it can offer the possibility of evaluating quality of traditional Chinese medicines following the overall principle. Chemometric techniques introduce multivariate analytical methods into fingerprinting to delve more information that is useful, which is consistent with the holistic thought and plays an important role in research on the substantial basis. In this review, we will start with three aspects to expound the quality evaluation of traditional Chinese medicines based on fingerprints. The analytical techniques used in developing fingerprints including chromatographic methods, spectroscopic methods and capillary electrophoresis are introduced. Strategies for fingerprints analysis usually based on chemometric methods including unsupervised pattern recognition and supervised pattern recognition are described. Applications of fingerprints for multi‐component quantification, quality control, screening of bioactive components and fingerprint‐efficacy relationship study are also outlined. Finally, we propose challenges and future perspectives of fingerprints in quality evaluation to promote the development of modernization and internationalization of traditional Chinese medicines. This article is protected by copyright. All rights reserved
Chapter
The open field test is used in studies of the neurobiological basis of anxiety and screening for novel drug targets and anxiolytic compounds. This test uses a camera to measure movement of the test animal in the peripheral and central zones of a 42 × 42 × 42 cm polyvinyl chloride box. This chapter describes a protocol for carrying out the open-field test for assessment of locomotion and anxiety-like behavior in mice.
Article
Sceletium tortuosum (Aizoaceae) is widely recognised for the treatment of stress, anxiety and depression, as well as for obsessive compulsive disorders. A comprehensive intraspecies chemotypic variation study, using samples harvested from two distinct regions of South Africa, was done using both proton nuclear magnetic resonance (1H-NMR) spectroscopy of methanol extracts (N = 145) and ultra performance liquid chromatography-mass spectrometry (UPLC-MS) of acid/base extracts (N = 289). Chemometric analysis of the 1H-NMR data indicated two main clusters that were region-specific (Northern Cape and Western Cape provinces). Two dimensional (2D) NMR was used to identify analytes that contributed to the clustering as revealed by the S-plot. The sceletium alkaloids, pinitol and two alkylamines, herein reported for the first time from S. tortuosum, were identified as markers that distinguished the two groups. Relative quantification of the marker analytes conducted by qNMR indicated that samples from the Northern Cape generally contained higher concentrations of all the markers than samples from the Western Cape. Quantitative analysis of the four mesembrine alkaloids using a validated UPLC-photo diode array (PDA) detection method confirmed the results of qNMR with regard to the total alkaloid concentrations. Samples from the Northern Cape Province were found to contain, on average, very high total alkaloids, ranging from 4938.0 to 9376.8 mg/kg dry w. Regarding the Western Cape samples, the total yields of the four mesembrine alkaloids were substantially lower (averages 16.4-4143.2 mg/kg). Hierarchical cluster analysis of the UPLC-MS data, based on the alkaloid chemistry, revealed three branches, with one branch comprising samples primarily from the Northern Cape that seemed somewhat chemically conserved, while the other two branches represented mainly samples from the Western Cape. The construction of an orthogonal projections to latent structures-discriminant analysis model and subsequent loadings plot, allowed alkaloid markers to be identified for each cluster. The diverse sceletium alkaloid chemistry of samples from the three clusters may facilitate the recognition of alkaloid profiles, rather than individual compounds, that exert targeted effects on various brain receptors involved in stress, anxiety or depression.
Article
This paper provides a 10‐year update of the 2007 systematic review of herbal medicines studied in a broad range of psychiatric disorders, including depression, anxiety, obsessive–compulsive, seasonal affective, bipolar, psychotic, phobic, somatoform, and attention‐deficit hyperactivity disorders. Ovid Medline, PubMed, and the Cochrane Library were searched for herbal medicines with both pharmacological and clinical evidence of psychotropic activity. This updated review now covers clinical trial evidence for 24 herbal medicines in 11 psychiatric disorders. High‐quality evidence was found to exist for the use of Piper methysticum (Kava), Passiflora spp. (passionflower) and Galphimia glauca (galphimia) for anxiety disorders; and Hypericum perforatum (St John's wort) and Crocus sativus (saffron) for major depressive disorder. Other encouraging herbal medicines with preliminary evidence include Curcuma longa (turmeric) in depression, Withania somnifera (ashwagandha) in affective disorders, and Ginkgo biloba (ginkgo) as an adjunctive treatment in Schizophrenia. Although depression and anxiety are commonly researched, many other mental disorders still require further prospective investigation. Although the previous review suggested increasing the adjunctive study of select herbal medicines with pharmaceuticals, this was still only found to sparingly occur in research designs. Aside from this, future focus should involve the incorporation of more biomarker analysis, in particular pharmacogenomics, to determine genetic factors moderating response to herbal medicines.
Article
The link between obesity-induced systemic inflammation and decreased insulin signalling is well-known. It is also known that peripherally produced inflammatory cytokines can cross the blood-brain barrier, resulting in the release of neurotoxins that can ultimately lead to the demise of central nervous system integrity. A high-mesembrine Sceletium tortuosum extract was recently shown to possess cytoprotective and mild anti-inflammatory properties in monocytes and to target specific p450 enzymes to reduce adrenal glucocorticoid synthesis. This is significant since the aetiology of both obesity and diabetes is linked to inflammation and excess glucocorticoid production. Given the interlinked nature of glucocorticoid action and inflammation, central immunomodulatory effects of two Sceletium tortuosum extracts prepared by different extraction methods were investigated. Human astrocytes were pre-treated for 30 min, before exposure to Escherichia coli lipopolysaccharide for 23.5 h (in the presence of treatment). Cytotoxicity, mitotoxicity and cytokine responses (basally and in response to inflammatory stimulus) were assessed. In addition, total polyphenol content, antioxidant capacity and selected neural enzyme inhibition capacity were assessed for both extracts. The high-mesembrine Sceletium extract exerted cytoprotective and anti-inflammatory effects. In contrast, the high delta7-mesembrenone extract, rich in polyphenols, exhibited potent antioxidant effect, although with relatively higher risk of adverse effects with overdose. We conclude that both Sceletium tortuosum extracts may be employed as either a preventative supplement or complimentary treatment in the context of obesity and diabetes; however, current data also highlights the impact that extraction methods can have on plant product mechanism of action.
Article
A number of factors (biogenic amine deficiency, genetic, environmental, immunologic, endocrine factors and neurogenesis) have been identified as mechanisms which provide unitary explanations for the pathophysiology of depression. Rather than a unitary construct, the combination and linkage of these factors have been implicated in the pathogenesis of depression. That is, environmental stressors and heritable genetic factors acting through immunologic and endocrine responses initiate structural and functional changes in many brain regions, resulting in dysfunctional neurogenesis and neurotransmission which then manifest as a constellation of symptoms which present as depression.
Article
Ethnopharmacological relevance: Sceletium tortuosum, among other Sceletium species, was traditionally used by the Khoisan people of Southern Africa for relief of pain-related ailments. However, the commercial availability of this supplement has greatly expanded due to anecdotal claims of its mood-elevating and anxiolytic properties. Unrelated research has elucidated a significant link between cytokines and the mediation of depression. Therefore, the effect of Sceletium supplementation on immune cell functionality is of interest, since the efficacy of potential depression treatments could, at least in part, rely on downregulation of pro-inflammatory signalling. Aim of the study: The current study evaluated the immunomodulatory effects of a Sceletium extract, both basally and in the context of acute endotoxin stimulation. Materials and methods: Primary human monocytes were supplemented with either a 0.01mg/ml or 1mg/ml Sceletium extract dose, with or without E. coli LPS stimulation in vitro, for 24hours. Mitochondrial viability, as an indirect measure of cytotoxicity, and cytokine release in response to the treatment intervention were assessed. Results: Sceletium extract treatment was associated with increased mitochondrial viability, as well as up-regulated IL-10 release under basal conditions. LPS exposure significantly decreased mitochondrial viability, but this was prevented completely under Sceletium-treated conditions. The acute inflammatory response to LPS stimulation was not negatively affected. Sceletium treatment conferred most significant effects at a dose of 0.01mg/ml. Conclusions: Sceletium exerts significant cytoprotective effects in the setting of endotoxin stimulation. Cytokine assessment indicated that Sceletium possesses mild anti-inflammatory properties, but does not hinder the mounting of an adequate immune response to acute immune challenge. These findings indicate that Sceletium may be beneficial for the attenuation of cytokine-induced depression, as well as in systemic low-grade inflammation.
Article
An estimated 50% of depressed patients are inadequately treated by available interventions. Even with an eventual recovery, many patients require a trial and error approach, as there are no reliable guidelines to match patients to optimal treatments and many patients develop treatment resistance over time. This situation derives from the heterogeneity of depression and the lack of biomarkers for stratification by distinct depression subtypes. There is thus a dire need for novel therapies. To address these known challenges, we propose a multi-scale framework for fundamental research on depression, aimed at identifying the brain circuits that are dysfunctional in several animal models of depression as well the changes in gene expression that are associated with these models. When combined with human genetic and imaging studies, our preclinical studies are starting to identify candidate circuits and molecules that are altered both in models of disease and in patient populations. Targeting these circuits and mechanisms can lead to novel generations of antidepressants tailored to specific patient populations with distinctive types of molecular and circuit dysfunction.
Article
Major Depressive Disorder (MDD) is one of the most common and debilitating mental disorders; however its etiology remains unclear. This paper aims to summarize the major neurobiological underpinnings of depression, synthesizing the findings into a comprehensive integrated view. A literature review was conducted using Pubmed. Search terms included “depression” or “MDD” AND “biology," “neurobiology," “inflammation," “neurogenesis," “monoamine," and “stress." Articles from 1995-2016 were reviewed with a focus on the connection between different biological and psychological models. Some possible pathophysiological mechanisms of depression include altered neurotransmission, HPA axis abnormalities involved in chronic stress, inflammation, reduced neuroplasticity, and network dysfunction. All of these proposed mechanisms are integrally related and interact bidirectionally. In addition, psychological factors have been shown to have a direct effect on neurodevelopment, causing a biological predisposition to depression, while biological factors can lead to psychological pathology as well. The authors suggest that while it is possible that there are several different endophenotypes of depression with distinct pathophysiological mechanisms, it may be helpful to think of depression as one united syndrome, in which these mechanisms interact as nodes in a matrix. Depressive disorders are considered in the context of the RDoC paradigm, identifying the pathological mechanisms at every translational level, with a focus on how these mechanisms interact. Finally, future directions of research are identified.
Article
Ethnopharmacological relevance: Mesembrine alkaloids are considered to be the primary active constituents of the South African medicinal plant Sceletium tortuosum (L.) N.E.Br. (Aizoaceae), and it is used as the dried or fermented aerial material from the plant, which is known as kanna (aka, channa, kougoed). Traditional regional use ranged from relieving thirst, mild analgesia, and alteration of mood. Current interest has focused primarily on the antidepressant action of preparations based on the plant and commercialization is expanding the recognition and availability of these preparations. Materials and methods: Searches for the keywords "Sceletium or mesembrine" were performed in "PubMed-NCBI", "Chemical Abstracts SciFinder" and "Thomson Reuters Web of Science" databases in addition to the inclusion of references cited within prior reviews and scientific reports. Additionally the "SciFinder" database was searched using 3a-phenyl-cis-octahydroindole in the SciFinder Substructure Module (SSM). Plant taxonomy was validated by the database "The Plant List". Results: This review focuses on the chemistry, analysis, and pharmacology of the mesembrine alkaloids. Despite a long history of medicinal used and research investigation, there has been a renewed interest in the pharmacological properties of the mesembrine alkaloids and much of the pharmacology has only recently been published. The two major active alkaloids mesembrine and mesembrenone are still in the process of being more fully characterized pharmacologically. They are serotonin reuptake inhibitors, which provides a rationale for the plant's traditional use as an antidepressant, but other actions are beginning to appear in the literature. Additionally, mesembrenone has reasonably potent PDE4 inhibitory activity. This review intends to provide an overview of the available literature, summarize the current findings, and put them in perspective with earlier studies and reviews.
Article
Depression involves deficits in monoaminergic neurotransmission. Differential roles for α2A, B and C subtypes of the α2-adrenoceptor (AR) are evident, with selective α2C-AR antagonists purported to have antidepressant and procognitive properties. However, this has not been demonstrated in a genetic animal model of depression. The role of the α2C-AR in modulating two key depression-related behaviours in the Flinders Sensitive Line (FSL) rat was studied using a dose-response analysis following subcutaneous administration with the selective α2C-AR antagonist ORM-10921 (0.03; 0.3 mg/kg), the nonselective α2-AR antagonist idazoxan (3 mg/kg), or vehicle once daily for 14 days. Behaviour in the novel object recognition test, forced swim test (FST) and locomotor activity test was assessed. To ratify the validity of the FSL model, the reference tricyclic antidepressant imipramine (15 mg/kg, intraperitoneally) was used as a comparator drug in the FST. FSL rats demonstrated significantly increased immobility and recognition memory deficits versus Flinders Resistant Line controls, with imipramine significantly reversing said immobility. Similarly, ORM-10921 at both doses but not idazoxan significantly reversed immobility in the FST as well as attenuated cognitive deficits in FSL animals. We conclude that selective α2C-AR antagonism has potential as a novel therapeutic strategy in the treatment of depression and cognitive dysfunction.
Article
Objective: Co-morbid depression with post-traumatic stress disorder (PTSD) is often treatment resistant. In developing a preclinical model of treatment-resistant depression (TRD), we combined animal models of depression and PTSD to produce an animal with more severe as well as treatment-resistant depressive-like behaviours. Methods: Male Flinders sensitive line (FSL) rats, a genetic animal model of depression, were exposed to a stress re-stress model of PTSD [time-dependent sensitisation (TDS)] and compared with stress-naive controls. Seven days after TDS stress, depressive-like and coping behaviours as well as hippocampal and cortical noradrenaline (NA) and 5-hydroxyindoleacetic acid (5HIAA) levels were analysed. Response to sub-chronic imipramine treatment (IMI; 10 mg/kg s.c.×7 days) was subsequently studied. Results: FSL rats demonstrated bio-behavioural characteristics of depression. Exposure to TDS stress in FSL rats correlated negatively with weight gain, while demonstrating reduced swimming behaviour and increased immobility versus unstressed FSL rats. IMI significantly reversed depressive-like (immobility) behaviour and enhanced active coping behaviour (swimming and climbing) in FSL rats. The latter was significantly attenuated in FSL rats exposed to TDS versus unstressed FSL rats. IMI reversed reduced 5HIAA levels in unstressed FSL rats, whereas exposure to TDS negated this effect. Lowered NA levels in FSL rats were sustained after TDS with IMI significantly reversing this in the hippocampus. Conclusion: Combining a gene-X-environment model of depression with a PTSD paradigm produces exaggerated depressive-like symptoms that display an attenuated response to antidepressant treatment. This work confirms combining FSL rats with TDS exposure as a putative animal model of TRD.
Article
Ethnopharmacological relevance: Sceletium tortuosum (L.) N.E. Br. has been reported to elevate mood, reduce anxiety and stress and alleviate pain. Aim of study: This study sought to examine the effects of an S. tortuosum alkaloid enriched fraction in the chick anxiety-depression model, a model that shows high predictive validity as a pharmacological screening assay. Material and methods: Socially-raised male Silver Laced Wyandotte chicks (4-6 days old) were given IP vehicle, imipramine (10mg/kg), or S. tortuosum fraction (10, 20, 30mg/kg in Exp. 1 or 50, 75, 100mg/kg in Exp. 2) 15min prior to a 60m isolation test period in which distress vocalizations (DVoc) were continuously recorded. Results: Vehicle chicks displayed high DVoc rates in the anxiety phase (first 3m). DVoc rates declined about 50% (i.e., behavioral despair) in the depression phase (30-60m). S. tortuosum fraction at 75 and 100mg/kg decreased DVoc rates during the anxiety phase indicative of an anxiolytic effect. Imipramine, but not S. tortuosum groups, increased DVoc rates in the depression phase indicative of an antidepressant effect. Conclusions: The findings suggest that an alkaloid enriched S. tortuosum fraction may benefit some forms of stress-related disorders.
Article
Background: People exposed to stressful experience are at increased risk of the development of depression. A number of functional imaging studies have found disturbances in the mood-regulating circuit of the stress-exposed depressed patients, although few animal imaging studies have been undertaken addressing the brain functional changes of depression. Methods: Two rat models of depression: maternal separation (MS) and chronic unpredictable mild stress (CUMS), imitating early life stress and adult stress respectively, were administered with escitalopram. The differences in functional brain changes were determined by blood oxygen level-dependent (BOLD) functional magnetic resonance imaging (fMRI). Results: Increased BOLD activation was observed in some brain regions of MS and CUMS animals, such as the bilateral hypothalamus, limbic system, hippocampus and frontal lobe, which were parts of mood-regulating circuit. Furthermore, the MS- and CUMS-induced increases in BOLD activation were partially attenuated by chronic escitalopram treatment. Conclusions: These results suggested hyperactivation of mood-regulating circuit at baseline in the depressed animals exposed to stressful experience, and escitalopram can at least partially reverse these effects.
Article
Anxiety and depression are complex heterogeneous psychiatric disorders and leading causes of disability worldwide. This review summarizes reports on the fundamentals, prevalence, diagnosis, neurobiology, advancement in treatment of these disease and preclinical assessment of botanicals. This review was conducted through bibliographic investigation of scientific journals, books, electronic sources, unpublished theses and electronic medium such as ScienceDirect, PubMed, etc. Number of the first line drugs (benzodiazepine, azapirone, antidepressant tricyclics, monoamine oxidase inhibitors, serotonin selective reuptake inhibitors, noradrenaline reuptake inhibitors, serotonin and noradrenaline reuptake inhibitors, etc.) for the treatment of these psychiatric disorders are products of serendipitous discoveries. In spite of the numerous classes of drugs that are available for the treatment of anxiety and depression, full remission has remained elusive. The emerging clinical cases have shown increasing interests among health practitioners and patients in phytomedicine. The development of anxiolytic and antidepressant drugs of plant origin takes advantage of multidisciplinary approach including but not limited to ethnopharmacological survey (careful investigation of folkloric application of medicinal plant), phytochemical and pharmacological studies. The selection of a suitable plant for a pharmacological study is a basic and very important step. Relevant clue to achieving this step include traditional use, chemical composition, toxicity, randomized selection or a combination of several criteria. Medicinal plants have been and continue to be a rich source of biomolecule with therapeutic values for the treatment of anxiety and depression. This article is protected by copyright. All rights reserved.
Article
Emerging evidence from case reports suggests that fentanyl may precipitate potentially life-threatening serotonin syndrome in patients taking serotonergic drugs. However, the underlying mechanism of the association between serotonin syndrome and fentanyl remains under investigation. We therefore investigated the pharmacological effects of an analgesic dose of fentanyl (0.2 mg/kg) injected subcutaneously (s.c.) on serotonergic toxicity-like responses in rats. Rats were s.c. injected with 0.75 mg/kg 8-OH-DPAT, a full 5-HT1A agonist, as an animal model of serotonin syndrome. The 8-OH-DPAT-treated rats showed well-characterized serotonin syndrome-like behaviors (low body posture, forepaw treading), hyperlocomotion, and decreased body temperature. Rats injected s.c. with fentanyl alone showed no significant changes in any of the parameters measured, while concomitant administration of fentanyl + 8-OH-DPAT resulted in exaggerated 8-OH-DPAT-induced serototoxic responses. A separate dose-response experiment showed that the serototoxic effect of fentanyl was dose-dependent. Pretreatment with naloxone [2.0 mg/kg, intraperitoneal (i.p.) injection], an opioid receptor antagonist, failed to antagonize the fentanyl-induced exaggerated serotonin syndrome-like behaviors. In contrast, pretreatment with WAY-100653, a serotonin 5-HT1A receptor antagonist (0.5 mg/kg, i.p. injection) completely inhibited all responses. Our findings provide preclinical proof-of-concept that an analgesic dose of fentanyl enhances serotonin toxicity, likely via its serotonin-reuptake inhibitory activity, independently of interaction with the opioid receptors.
Article
Escitalopram (Cipralex®, Lexapro™), the active S-enantiomer of the racemic selective serotonin reuptake inhibitor (SSRI) citalopram (RS-citalopram), is a highly selective inhibitor of the serotonin transporter protein. It possesses a rapid onset of antidepressant activity, and is an effective and generally well tolerated treatment for moderate-to-severe major depressive disorder (MDD). Pooled analyses from an extensive clinical trial database suggest that escitalopram is consistently more effective than citalopram in moderate-to-severe MDD. Preliminary studies suggest that escitalopram is as effective as other SSRIs and the extended-release (XR) formulation of the serotonin/noradrenaline (norepinephrine) reuptake inhibitor venlafaxine, and may have cost-effectiveness and cost-utility advantages. However, additional longer-term, comparative studies evaluating specific efficacy, tolerability, health-related quality of life and economic indices would be helpful in definitively positioning escitalopram relative to these other agents in the treatment of MDD. Nevertheless, available clinical and pharmacoeconomic data indicate that escitalopram is an effective first-line option in the management of patients with MDD. Pharmacological Properties Unlike other SSRIs, escitalopram appears to not only bind to a primary high-affinity site on the serotonin transporter protein, but also to a secondary, lower-affinity allosteric site that is considered to stabilise and prolong drug binding. In vitro, escitalopram was approximately twice as potent as citalopram in inhibiting serotonin reuptake and, in radioligand binding assays, it was more selective than other SSRIs, including citalopram, for the human serotonin transporter protein. Escitalopram has shown no or very low affinity for various other receptors in vitro. In vivo, escitalopram was four times more potent than citalopram at reducing firing activity of presumed serotonergic neurons in the dorsal raphe nucleus in rat brain. The multiple-dose pharmacokinetic profile of escitalopram is linear across a 10–30 mg/day dosage (20 mg/day is the maximum approved dosage). Steady-state plasma concentrations are achieved after about 7–10 days’ administration of escitalopram 10 mg/day. The absolute oral bioavailability of escitalopram is about 80%, and protein binding, which is independent of escitalopram plasma concentrations, is ≈55%. Concurrent food ingestion has no influence on escitalopram pharmacokinetics. Escitalopram is extensively metabolised in the liver. In vitro, the cytochrome P450 isoenzymes 2C19, 3A4 and 2D6 contribute equally to its metabolism. The main metabolite is S-demethylcitalopram, which is further metabolised to S-didemethylcitalopram. Both metabolites have virtually no serotonin reuptake activity in vivo. Escitalopram and metabolites are primarily renally excreted, with only a small percentage eliminated as unchanged drug. The plasma elimination half-life is ≈27–33 hours. Escitalopram dosage adjustments are advocated in elderly patients and those with hepatic impairment, and caution should be exercised with escitalopram use in patients with severe renal impairment. Therapeutic Efficacy In well designed, comparative studies with placebo and/or citalopram in patients with moderate-to-severe MDD, escitalopram was more effective than placebo and at least as effective as citalopram in reducing the mean Montgomery-Åsberg Depression Rating Scale (MADRS) total score from baseline (primary efficacy parameter). In large, pooled analyses in patients with moderate-to-severe MDD, escitalopram was consistently more effective than placebo or citalopram in terms of a faster onset of antidepressant activity, greater decreases in mean MADRS total score and mean Clinical Global Impression-Severity score, and superior rates of response (percentage of patients with a ≥50% decrease in MADRS score) and remission (percentage of patients attaining a MADRS score ≤12). Several randomised, double-blind studies in patients with moderate-to-severe MDD showed that escitalopram was as effective as paroxetine, sertraline or venlafaxine XR in reducing MADRS scores. Escitalopram demonstrated continued efficacy in a 52-week open-label extension of two 8-week double-blind studies in primary-care patients with moderate-to-severe MDD, and significantly prevented relapse in 36- and 52-week double-blind, placebo-controlled studies. Modelled pharmacoeconomic evaluations and a prospective pharmacoeconomic analysis suggested cost-effectiveness advantages for escitalopram relative to several other SSRIs and venlafaxine (including the XR formulation). Cost utility analyses showed that escitalopram dominated all the other treatments. A potential for cost savings (up to 4.5%) was shown in total healthcare budgets for depression when escitalopram is introduced. Tolerability In placebo-controlled studies, the most common treatment-emergent adverse events with escitalopram were nausea (15%), ejaculation disorder (9%), insomnia (9%), diarrhoea (8%), somnolence (7%), dry mouth (6%) and dizziness (6%). Nausea led to withdrawal of 2% of patients and 2% of men withdrew because of ejaculation disorder. Large-scale comparisons of escitalopram with citalopram revealed that the overall type and incidence of adverse events were generally similar between treatments. Escitalopram demonstrated a lower incidence of nausea, increased sweating and constipation than venlafaxine XR. Discontinuation syndrome (Discontinuation Emergent Signs and Symptoms score increase of ≥4) was seen in fewer escitalopram than venlafaxine XR recipients after treatment withdrawal Likewise, in comparisons with paroxetine, fewer escitalopram recipients had discontinuation syndrome after treatment cessation. The tolerability profile of escitalopram was generally similar to that of fluoxetine in elderly patients and to that of sertraline in patients aged 18–80 years. A large meta-analysis of data from placebo-controlled studies specific to the use of escitalopram revealed that no suicides with the drug occurred within the first 2 weeks or throughout up to 24 weeks of therapy. In addition, MADRS item-10 (‘suicidal thoughts’) scores were reduced compared with placebo from the first week in 8-week studies. Pharmacovigilance data reveal a very low suicide rate of 1.8 per 1 million patients treated with escitalopram.
Article
Despite significant research efforts aimed at understanding the neurobiological underpinnings of mood (depression, bipolar disorder) and psychotic disorders, the diagnosis and evaluation of treatment of these disorders are still based solely on relatively subjective assessment of symptoms as well as psychometric evaluations. Therefore, biological markers aimed at improving the current classification of psychotic and mood-related disorders, and that will enable patients to be stratified on a biological basis into more homogeneous clinically distinct subgroups, are urgently needed. The attainment of this goal can be facilitated by identifying biomarkers that accurately reflect pathophysiologic processes in these disorders. This review postulates that the field of psychotic and mood disorder research has advanced sufficiently to develop biochemical hypotheses of the etiopathology of the particular illness and to target the same for more effective disease modifying therapy. This implies that a “one-size fits all” paradigm in the treatment of psychotic and mood disorders is not a viable approach, but that a customized regime based on individual biological abnormalities would pave the way forward to more effective treatment. In reviewing the clinical and preclinical literature, this paper discusses the most highly regarded pathophysiologic processes in mood and psychotic disorders, thereby providing a scaffold for the selection of suitable biomarkers for future studies in this field, to develope biomarker panels, as well as to improve diagnosis and to customize treatment regimens for better therapeutic outcomes.
Article
We need to make substantial changes to how we conduct research. First, in response to heightened concern that our published research literature is incomplete and untrustworthy, we need new requirements to ensure research integrity. These include prespecification of studies whenever possible, avoidance of selection and other inappropriate data-analytic practices, complete reporting, and encouragement of replication. Second, in response to renewed recognition of the severe flaws of null-hypothesis significance testing (NHST), we need to shift from reliance on NHST to estimation and other preferred techniques. The new statistics refers to recommended practices, including estimation based on effect sizes, confidence intervals, and meta-analysis. The techniques are not new, but adopting them widely would be new for many researchers, as well as highly beneficial. This article explains why the new statistics are important and offers guidance for their use. It describes an eight-step new-statistics strategy for research with integrity, which starts with formulation of research questions in estimation terms, has no place for NHST, and is aimed at building a cumulative quantitative discipline.
Article
Obsessive-compulsive disorder (OCD) is characterized by recurrent thoughts and repetitive motor actions. Hyposerotonergic signalling in the cortico-striatal circuitry is believed to be central to the pathology of OCD, while many patients only respond to chronic treatment with high dose selective serotonin (5HT) reuptake inhibitors (SSRIs). Confined deer mice spontaneously develop two forms of stereotypy, namely vertical jumping and pattern running. The purpose of this investigation was to reappraise these behaviours and strengthen the validity of deer mouse stereotypy as an animal model of OCD within a framework of three study questions: 1) can the time spent executing stereotypical behaviours be employed as a measure of extent of stereotypy, 2) does deer mouse stereotypy only respond to chronic, but not sub-chronic treatment with a high-dose SSRI, and 3) is deer mouse stereotypy associated with altered cortico-striatal SERT binding?The current study demonstrates that treatment naïve high stereotypical (HS) deer mice spend significantly more time executing stereotypical behaviours while significantly less time is spent indulging in stereotypy following chronic, but not sub-chronic,treatment with escitalopram. Furthermore, HS deer mice present with a significant decrease in striatal SERT density compared to the non-stereotypical (NS) controls. Building on previous validation studies, we conclude that deer mouse stereotypy is a valid naturalistic animal model of OCD with robust face, construct and predictive validity.
Article
Side effects of antidepressants are usually underreported in clinical trials and large scale naturalistic studies are restricted to six months of use. We examined the prevalence and nature of patient-perceived side effects and their determinants during long-term antidepressant use in a naturalistic setting. Subjects, aged 19 to 67 years, in the Netherlands Study of Depression and Anxiety were recruited from primary care and specialized mental health care covered 927 cases of single antidepressant use. In 64% of cases, on average, 2.9 side effects were reported. The number of side effects was higher when subjects had higher depression severity (OR=1.28; p=0.002), three or more psychiatric diagnoses (OR=1.97; p=0.02), higher dose (OR=1.44; p=0.006) and was lower when subjects were older (OR=0.83; p=0.02) and had longer duration of use (OR=0.94; p=0.04). Tricyclic antidepressants were associated with more side effects (OR=2.52; p=0.003) and, particularly, more anticholinergic effects, like dry mouth and constipation, as compared to selective serotonin reuptake inhibitors. Venlafaxine showed more profuse sweating (OR=1.79; p=0.007), whereas mirtazapine showed more weight gain and less sexual dysfunction (OR=0.36; p=0.03), as compared to selective serotonin reuptake inhibitors. Weight gain was associated with female gender (OR=1.76; p=0.004) and duration of use (OR=1.06; p=0.03). We show that antidepressant side effect, known from short-term studies, persist during long-term use and are associated with depression severity and antidepressant dose. A novel finding was that venlafaxine is associated with more profuse sweating and that weight gain appeared more specific in female users. Clinicians should be aware that, during long-term antidepressant use, side effects are common and persistent.
Article
Approximately 25 years have passed since the first publication suggesting the Flinders sensitive line (FSL) rat as an animal model of depression. At least 6 years of research on these rats was completed before that seminal paper, and there has been a steady stream of publications (130+) over the years. The present review will focus on several issues not previously covered in earlier reviews, summarize the several lines of ongoing investigations, and propose a novel mechanism that accounts for a number of previously unexplained observations. A key observation in the FSL rat relates to the antidepressant (AD)-like effects of known and putative antidepressants. The FSL rat typically exhibits an AD-like effect in behavioral tests for AD-like activity following chronic (14 days) treatment, although some studies have found AD-like effects after fewer days of treatment. In other observations, exaggerated swim test immobility in the FSL rat has been found to have a maternal influence, as shown by cross-fostering studies and observations of maternal behavior; the implications of this finding are still to be determined. Ongoing or recently completed studies have been performed in the laboratories of Marko Diksic of Canada, Aleksander Mathé of Sweden, Gregers Wegener of Denmark, Brian Harvey of South Africa, Paul Pilowsky and Rod Irvine of Australia, and Gal Yadid of Israel. Jennifer Loftis of Portland, Oregon, and Lynette Daws of San Antonio, Texas, have been working with the FSL rats in the United States. A puzzling feature of the FSL rat is its sensitivity to multiple chemicals, and its greater sensitivity to a variety of drugs with different mechanisms of action. It has been recently shown that each of these drugs feeds through G protein-coupled receptors to potassium-gated channels. Thus, an abnormality in the potassium channel could underlie the depressed-like behavior of the FSL rats.
Article
Animal models and preclinical tests have played large roles in the development of antidepressant drugs and are likely to continue to play important roles. In the present communication, the main animal models of depression have been described and reviewed. These models include the Flinders sensitive line (FSL) rat, the Wistar Kyoto (WKY) rat, the fawn-hooded (FH) rat, and the learned helpless (LH) rat. In addition, the materials used to assess the behavior of these rats, including swim tanks, drinking tubes, and an open field apparatus, have been discussed. Finally, the methods used in collecting the relevant behaviors in the animal models are described. These include the procedures used in the forced swim test and chronic mild stress protocols, including the sucrose preference test. It is concluded that the behavioral tests used to infer depressed-like behavior in rats will continue to provide useful data if the appropriate animals and proper methods are used.
Article
Sceletium tortuosum is an indigenous South African plant that has traditionally been used for its mood-enhancing properties. Recently, products containing S. tortuosum have become increasingly popular and are commonly administered as tablets, capsules, teas, decoctions, or tinctures, while traditionally the dried plant material has been masticated. This study evaluated the in vitro permeability of the four major S. tortuosum alkaloids (i.e., mesembrine, mesembrenone, mesembrenol, and mesembranol) across porcine intestinal, sublingual, and buccal tissues in their pure form and in the form of three different crude plant extracts, namely water, methanol, and an acid-base alkaloid-enriched extract. The permeability of mesembrine across intestinal tissue was higher than that of the highly permeable reference compound caffeine (which served as a positive control for membrane permeability) both in its pure form, as well as in the form of crude extracts. The intestinal permeability of mesembranol was similar to that of caffeine, while those of mesembrenol and mesembrenone were lower than that of caffeine, but much higher than that of the poorly permeable reference compound atenolol (which served as a negative control for membrane permeability). In general, the permeabilities of the alkaloids were lower across the sublingual and the buccal tissues than across the intestinal tissue. However, comparing the transport of the alkaloids with that of the reference compounds, there are indications that transport across the membranes of the oral cavity may contribute considerably to the overall bioavailability of the alkaloids, depending on pre-systemic metabolism, when the plant material is chewed and kept in the mouth for prolonged periods. The results from this study confirmed the ability of the alkaloids of S. tortuosum in purified or crude extract form to permeate across intestinal, buccal, and sublingual mucosal tissues.
Article
Escitalopram is a widely used antidepressant for the treatment of patients with major depression. It is the pure S-enantiomer of racemic citalopram. Several clinical trials and meta-analyses indicate that escitalopram is quantitatively more efficacious than many other antidepressants with a faster onset of action. This paper reviews current knowledge about the mechanism of action of escitalopram. The primary target for escitalopram is the serotonin transporter (SERT), which is responsible for serotonin (or 5-hydroxytryptamine [5-HT]) reuptake at the terminals and cell bodies of serotonergic neurons. Escitalopram and selective serotonin reuptake inhibitors bind with high affinity to the 5-HT binding site (orthosteric site) on the transporter. This leads to antidepressant effects by increasing extracellular 5-HT levels which enhance 5-HT neurotransmission. SERT also has one or more allosteric sites, binding to which modulates activity at the orthosteric binding site but does not directly affect 5-HT reuptake by the transporter. In vitro studies have shown that through allosteric binding, escitalopram decreases its own dissociation rate from the orthosteric site on the SERT. R-citalopram, the nontherapeutic enantiomer in citalopram, is also an allosteric modulator of SERT but can inhibit the actions of escitalopram by interfering negatively with its binding. Both nonclinical studies and some clinical investigations have demonstrated the cellular, neurochemical, neuroadaptive, and neuroplastic changes induced by escitalopram with acute and chronic administration. The findings from binding, neurochemical, and neurophysiological studies may provide a mechanistic rationale for the clinical difference observed with escitalopram compared to other antidepressant therapies.
Article
Early life stress is a potential precursor of eventual neuropsychiatric diseases and may result in altered neurodevelopment and function of the hippocampus, which thus provides a site at which potential interventions to modify the effects of early life stress may act. In this study, Sprague-Dawley rat pups comprising male and female animals underwent maternal separation (MS) for 180 min from postnatal days (PND) 2 to 14, or were left with their dams. They subsequently received daily administration of saline (0.9%), escitalopram (10 mg/kg), or no treatment during adolescence (PND 43-60). All adult animals underwent brain magnetic resonance imaging (MRI) and bilateral hippocampal proton magnetic resonance spectroscopy ((1)H-MRS). Neither MS nor escitalopram treatment had a significant effect on hippocampal volume. Adult rats that experienced MS displayed significantly increased choline-containing compounds (Cho) and decreased N-acetylaspartate (NAA), glutamate (Glu) and Myo-inositol (MI) relative to the stable neurometabolite creatine (Cr) in hippocampus. Administration of escitalopram during adolescence could modify the alterations of NAA/Cr, Glu/Cr and MI/Cr. The effects of MS on hippocampal neurochemistry were most significant in the right hippocampus. These results indicate that MS in rats has long-term consequences on hippocampal neurochemistry reflective of neural density/functional integrity, especially on the right hippocampus, and adolescent administration with escitalopram can at least partially ameliorate these neurochemical alterations. Furthermore, these metabolite changes seem to be more sensitive indicators of the results from early life stress than volume changes.