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A Common Neuroendocrine Substrate for Diverse General Anesthetics and Sleep

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Abstract

How general anesthesia (GA) induces loss of consciousness remains unclear, and whether diverse anesthetic drugs and sleep share a common neural pathway is unknown. Previous studies have revealed that many GA drugs inhibit neural activity through targeting GABA receptors. Here, using Fos staining, ex vivo brain slice recording, and in vivo multi-channel electrophysiology, we discovered a core ensemble of hypothalamic neurons in and near the supraoptic nucleus, consisting primarily of neuroendocrine cells, which are persistently and commonly activated by multiple classes of GA drugs. Remarkably, chemogenetic or brief optogenetic activations of these anesthesia-activated neurons (AANs) strongly promote slow-wave sleep and potentiates GA, whereas conditional ablation or inhibition of AANs led to diminished slow-wave oscillation, significant loss of sleep, and shortened durations of GA. These findings identify a common neural substrate underlying diverse GA drugs and natural sleep and reveal a crucial role of the neuroendocrine system in regulating global brain states. VIDEO ABSTRACT.

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... We recorded electroencephalography/electromyography (EEG/EMG) signals of Crbn YW/AA KI mice treated with thalidomide and determined whether thalidomide had a hypnotic effect in these mutants. We also studied the effect of thalidomide on the balance between synaptic excitation and inhibition in the brain, a typical mechanism for a range of hypnotics, and investigated immediate to early gene expression in hypothalamic areas known to be affected by classical sedatives (34). ...
... GABA A receptor-activating sedatives, such as benzodiazepines, produce hypothalamic Fos staining patterns similar to those observed in sleep (35). Drugs inducing general anesthesia also induce Fos expression in a core set of hypothalamic neurons (34). Anti-Fos immunoreactivity was assessed in brain slices obtained after thalidomide (200 mg/kg i.p.) treatment and compared with vehicle treatment. ...
... Recently, however, increased Fos expression was observed in the SON and para-SON regions after treatment with general anesthetics such as isoflurane, propofol, ketamine, and dexmedetomidine. Furthermore, selective activation of these Fos-positive neurons produced sleep (34). The resemblance of thalidomide-induced Fos expression patterns to those evoked by a number of general anesthetics suggests that thalidomide may activate a common hypothalamic pathway leading to sleep (34). ...
Article
Significance Thalidomide was introduced in 1950s as a safe and effective hypnotic but was subsequently withdrawn from the market due to its devastating teratogenicity in humans. More recently, thalidomide has reemerged as an antineoplastic and immunomodulatory medicine. The teratogenic and immunomodulatory effects of thalidomide have been attributed to direct inhibition of the cereblon-mediated ubiquitin/proteasome pathway. Here we show that cereblon is not involved in the hypnotic effect of thalidomide, using mice that carry a thalidomide-resistant mutant allele of the cereblon gene. Our results suggest the possibility for dissociating the hypnotic effect of thalidomide and its analogs from its teratogenicity.
... For example, varieties of neurons and their projections that are important to promote wakefulness, including monoaminergic [4,5], cholinergic [6], glutamatergic [7], and orexinergic neurons [8], participate in promoting emergence from general anesthesia. The γ-aminobutyric acid (GABA) neurons in the ventrolateral preoptic nucleus (VLPO) extensively innervate and suppress multiple arousal-promoting brain regions [9,10]. The VLPO is vital for both the initiation and maintenance of sleep [11]. ...
... When exploring the role of neural pathways that promote sleep in general anesthesia, Jiang et al. identified multiple anesthetic-activated neurons in the hypothalamic preoptic area, an area traditionally viewed as a regulatory sleep center. Chemogenetic activation of these neurons reliably produces slow-wave sleep and facilitates general anesthesia, and chemogenetic inhibition shortens the general anesthesia time and disrupts natural sleep [9]. Recent studies have found that chemogenetic activation of GABAergic neurons in other brain regions, such as the VTA [79] and RMTg [80], promotes an anesthesia state as well, whereas chemogenetic activation of dorsal-intermediate lateral septum GABAergic neurons contributes to anesthesia emergence [55]. ...
... Jiang et al. reported that optogenetic activation of anesthetics-activated neurons in the hypothalamus preoptic area accelerates sleep and enhances the effects of general anesthesia. In contrast, optogenetic inhibition of these neurons reduced the duration of general anesthesia [9]. Again, these results demonstrate that the hypothalamic preoptic area plays a crucial role in maintaining general anesthesia. ...
Article
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General anesthesia has been widely utilized since the 1840s, but its underlying neural circuits remain to be completely understood. Since both general anesthesia and sleep are reversible losses of consciousness, studies on the neural-circuit mechanisms affected by general anesthesia have mainly focused on the neural nuclei or the pathways known to regulate sleep. Three advanced technologies commonly used in neuroscience, in vivo calcium imaging, chemogenetics, and optogenetics, are used to record and modulate the activity of specific neurons or neural circuits in the brain areas of interest. Recently, they have successfully been used to study the neural nuclei and pathways of general anesthesia. This article reviews these three techniques and their applications in the brain nuclei or pathways affected by general anesthesia, to serve as a reference for further and more accurate exploration of other neural circuits under general anesthesia and to contribute to other research fields in the future.
... used [15,16]. To the best of our knowledge, except for c-fos, very few other IEG products have been used to detect neural activity to determine the neural basis of general anesthesia or sleep-arousal [17][18][19]. Therefore, in this review, we focused on studies that investigated the neural basis of mechanisms of action of general anesthetics based on a c-fos expression. ...
... The SON is part of the hypothalamic-pituitary axis and is located in the anterior hypothalamus [18,43]. The SON regulates many physiological functions related to osmotic balance and vasoconstriction [44]. ...
... Interestingly, a recent study reported that SON neurons are commonly activated by various classes of general anesthetics, including isoflurane (1%-1.2%), propofol (180 mg/kg), ketamine (100 mg/kg), and dexmedetomidine (100 μg/kg) determined by increased c-fos expression, recording of brain slices, and in vivo recording of multichannel electrophysiology [18]. In this study, a distinct cluster of SON neurons was identified with strong c-fos positivity in response to these general anesthetics. ...
Article
Although general anesthetics have been used in the clinic for more than 170 years, the ways in which they induce amnesia, unconsciousness, analgesia, and immobility remain elusive. Modulations of various neural nuclei and circuits are involved in the actions of general anesthetics. The expression of the immediate early gene c-fos and its nuclear product, c-fos protein can be induced by neuronal depolarization; therefore, c-fos staining is commonly used to identify the activated neurons during sleep and/or wakefulness, as well as in various physiological conditions in the central nervous system. Identifying c-fos expression is also a direct and convenient method to explore the effects of general anesthetics on the activity of neural nuclei and circuits. Using c-fos staining, general anesthetics have been found to interact with sleep- and wakefulness-promoting systems throughout the brain, which may explain their ability to induce unconsciousness and emergence from general anesthesia. This review summarizes the actions of general anesthetics on neural nuclei and circuits based on c-fos expression.
... PGD 2 has been identified as one of the most potent endogenous sleep-promoting molecules by stimulating the DP1 receptors on the ventral surface from the basal forebrain to the hypothalamus [135]. Recently, neuroendocrine cells in the supraoptic nucleus (SON) and paraSON (including the VLPO and POA) have been proved to strongly promote slow-wave sleep (SWS) of NREM [136], with the VLPO temperature-dependently producing PGD 2 [97] and the SON highly expressing PTGDS [137] and activated by endogenous PGD 2 [138]. It seems reasonable that the PTGDS-expressing neurons in the SON/POA copotentiate NREM sleep and hypothermia. ...
... In recent decades, optogenetic and chemogenetic manipulations enable us to specifically identify the neuronal populations and neural pathways related to states induced by general anesthesia ( Table 2). The most noteworthy is some non-classical locations that are found to co-regulate SWs and GAs, such as the thalamic reticular nucleus (TRN) [164], PVT [157], LHb [158], VTA [155,156,165,166] and PBN [167] as well as the neuroendocrine general-anesthesia-activated neurons (AANs) in the SON [136]. ...
... However, there still stand many questions. Firstly, the different EEG signatures produced by different kinds of anesthetics [33,162] as well as the different extents the AANs in the SON re-activated by different kinds of anesthetics [136] suggest that different anesthetics may act on different neuronal populations or neural pathways [163]. ...
Article
Great progress has been made in specifically identifying the central neural circuits (CNCs) of the core body temperature (Tcore), sleep-wakefulness states (SWs), and general anesthesia states (GAs), mainly utilizing optogenetic or chemogenetic manipulations. We summarize the neuronal populations and neural pathways of these three CNCs, which gives evidence for the orchestration within these three CNCs, and the integrative regulation of these three CNCs by different environmental light signals. We also outline some transient receptor potential (TRP) channels that function in the CNCs-Tcore and are modulated by some general anesthetics, which makes TRP channels possible targets for addressing the general-anesthetics-induced-hypothermia (GAIH). We suggest this review will provide new orientations for further consummating these CNCs and elucidating the central mechanisms of GAIH.
... 79,80 A recent study found a novel group of GABAergic and glutamatergic neurons in the supraoptic nucleus (SON) of the hypothalamus that was activated by multiple anesthetics and that promoted NREM sleep. 81 Using modern genetic techniques, the group also identified neurons that serve as a common substrate for both anesthesia and analgesia in the central amygdala, 82 illustrating the potential for new tools to advance our understanding of the neural circuitry underlying anesthesia and sleep. 83 Investigations of the lateral habenula (LHb), a region that modulates midbrain dopaminergic neurotransmission, have demonstrated its involvement in facilitating NREM sleep, 84,85 as well as maintaining circadian rhythms, [86][87][88] homeostatic sleep regulation, 89 and NREM sleep stability. ...
... 83 Recently, a new genetic technique of tracking, targeting, and stimulating specific neural populations has allowed the targeting of specific behavior-associated brain loci, including "anesthesia-activated neurons" (AANs) located in the SON of the hypothalamus. 81 These AANs were not only activated by a range of anesthetics, but their activation also promoted slow-wave sleep, illustrating the potential of these emerging techniques to further advance our knowledge of the neural circuitry underlying complex phenomena. Gaining insights into the neural circuitry underlying general anesthesia and sleep will likely lead to improved methods for controlling arousal states in the perioperative setting. ...
Article
General anesthesia is characterized by loss of consciousness, amnesia, analgesia, and immobility. Important molecular targets of general anesthetics have been identified, but the neural circuits underlying the discrete end points of general anesthesia remain incompletely understood. General anesthesia and natural sleep share the common feature of reversible unconsciousness, and recent developments in neuroscience have enabled elegant studies that investigate the brain nuclei and neural circuits underlying this important end point. A common approach to measure cortical activity across the brain is electroencephalogram (EEG), which can reflect local neuronal activity as well as connectivity among brain regions. The EEG oscillations observed during general anesthesia depend greatly on the anesthetic agent as well as dosing, and only some resemble those observed during sleep. For example, the EEG oscillations during dexmedetomidine sedation are similar to those of stage 2 nonrapid eye movement (NREM) sleep, but high doses of propofol and ether anesthetics produce burst suppression, a pattern that is never observed during natural sleep. Sleep is primarily driven by withdrawal of subcortical excitation to the cortex, but anesthetics can directly act at both subcortical and cortical targets. While some anesthetics appear to activate specific sleep-active regions to induce unconsciousness, not all sleep-active regions play a significant role in anesthesia. Anesthetics also inhibit cortical neurons, and it is likely that each class of anesthetic drugs produces a distinct combination of subcortical and cortical effects that lead to unconsciousness. Conversely, arousal circuits that promote wakefulness are involved in anesthetic emergence and activating them can induce emergence and accelerate recovery of consciousness. Modern neuroscience techniques that enable the manipulation of specific neural circuits have led to new insights into the neural circuitry underlying general anesthesia and sleep. In the coming years, we will continue to better understand the mechanisms that generate these distinct states of reversible unconsciousness.
... Lesions of cholinergic BF neurons increase the duration of LORR under propofol and pentobarbital but not halothane anesthesia (Leung et al., 2011). In regards to sleep promoting regions, activation of SON neurons that promote sleep also prolong emergence from isoflurane anesthesia (Jiang-Xie et al., 2019). Neurons in the POA are also capable of modulating anesthetic sensitivity, and will be discussed in more detail in the next section. ...
... Activation of wake-promoting PB neurons shortens time to emerge from both propofol and isoflurane anesthesia (Luo et al., 2018). Additionally, inhibition of sleep-promoting SON neurons has no effect on isoflurane induction, but does decrease time to emerge (Jiang-Xie et al., 2019). Finally, inhibition of wake-promoting orexinergic LH neurons has no effect on induction but delays emergence from both isoflurane and sevoflurane (Kelz et al., 2008). ...
Article
The role of the hypothalamic preoptic area (POA) in arousal state regulation has been studied since the early 20th century. Since then, the POA has been shown to modulate arousal in both natural (sleep and wake) as well as drug-induced (anesthetic-induced unconsciousness) states. While the POA is most known for its role in sleep promotion, populations of wake-promoting neurons within the region have also been identified. However, the complexity and molecular heterogeneity of the POA has made distinguishing these two populations difficult. Though multiple lines of evidence demonstrate that general anesthetics modulate the activity of the POA, the region’s heterogeneity has also made it challenging to determine whether the same neurons involved in sleep/wake regulation also modulate arousal in response to general anesthetics. While a number of studies show that sleep-promoting POA neurons are activated by various anesthetics, recent work suggests this is not universal to all arousal-regulating POA neurons. We hypothesized that the POA’s broad neuronal diversity could mask convergent roles of a subset of neurons in regulating both arousal and anesthesia. In this dissertation, we utilize a neuropeptide, tachykinin 1 (Tac1), as a molecular marker for arousal state-regulating POA neurons and show using EEG/EMG recordings that chemogenetic activation of these POA Tac1 neurons strongly promotes wakefulness over both NREM and REM sleep, consolidating the wake state for hours. Additionally, actigraphy and video recordings demonstrate that POA Tac1 activation increases locomotor activity, with no evidence of enhanced anxiety. We also show that activation of this same population stabilizes the wake state against both isoflurane- and sevoflurane-induced unconsciousness, producing a partial resistance to entering isoflurane anesthesia and a more pronounced ability to exit both isoflurane and sevoflurane hypnosis. Furthermore, activation of POA Tac1 neurons promotes resistance throughout prolonged exposures to isoflurane on both the population and individual level, further supporting their arousal-promoting role. Together, these results demonstrate that POA Tac1 neurons can potently reinforce arousal against both endogenous and drug-induced states of unconsciousness, identifying a subpopulation within the POA that may be shared between the circuits regulating sleep/wake and anesthesia.
... Furthermore, long-lasting peptidergic signaling has been reported to be vital for regulating GA-induced LOC. 31 NAc D1R neurons may facilitate the release of neuropeptides, and these neuropeptides may further influence multiple neural activities and work on a longer timescale. ...
... We further analyzed the real-time activities of NAc D1R neurons during the induction and emergence phases of 2% sevoflurane, from wakefulness to the LOC state or from LOC to the ROC state, as determined by EEG/EMG recordings. 31 We identified state transitions and aligned DF/F with a window of À180 s~+300 s before and after 2% sevoflurane being turned on or off. 37 The onset of LOC was defined as the transition from a low-amplitude, high-frequency EEG to a high-amplitude, low-frequency EEG, combined with ...
Article
Although general anesthesia (GA) enables patients to undergo surgery without consciousness, the precise neural mechanisms underlying this phenomenon have yet to be identified. In addition to many studies over the past two decades implicating the thalamus, cortex, brainstem, and conventional sleep-wake circuits in GA-induced loss of consciousness (LOC), some recent studies have begun to highlight the importance of other brain areas as well. Here, we found that population activities of neurons expressing dopamine D1 receptor (D1R) in the nucleus accumbens (NAc), a critical interface between the basal ganglia and limbic system, began to decrease before sevoflurane-induced LOC and gradually returned after recovery of consciousness (ROC). Chemogenetic activation of NAcD1R neurons delayed induction of and accelerated emergence from sevoflurane GA, whereas chemogenetic inhibition of NAcD1R neurons exerted opposite effects. Moreover, transient activation of NAcD1R neurons induced significant cortical activation and behavioral emergence during continuous steady-state GA with sevoflurane or deep anesthesia state with constant and stable burst-suppression oscillations. Taken together, our findings uncover that NAcD1R neurons modulated states of consciousness associated with sevoflurane GA and may represent an area for targeting GA-induced changes in consciousness and ameliorating related adverse effects.
... In addition to their sleep-promoting effects, VLPO neurons have also been implicated in the mechanisms of action of anaesthetic drugs (Moore et al., 2012;Zhang et al., 2015). Of note, recent evidence also indicates a common role of hypothalamic neuroendocrine cells of the mouse in sleep generation and general anaesthesia induced by several different anaesthetics, with opto-or chemo-genetic activation of these cells promoting both slow-wave sleep and anaesthesia, and the opposite result obtained by inhibiting them (Jiang-Xie et al., 2019). ...
... Given the shared pathways of dopaminergic and noradrenergic transmitter production, it seems plausible that these transmitters and their nuclei in the brainstem may act in-concert to produce wakefulness, and to counter the effects of sleep inertia and neural inertia, as evidenced by their influences on recovery and induction times. Likewise, the recent discovery that hypothalamic neuroendocrine cells are involved in both slow-wave sleep and general anaesthesia induced by multiple classes of anaesthetic drugs (Jiang-Xie et al., 2019) suggests that a fuller understanding of the link between sleep and neural inertia may benefit from taking into account neuroendocrine involvement. ...
Article
Full-text available
“Neural inertia” is the brain’s tendency to resist changes in its arousal state: it is manifested as emergence from anaesthesia occurring at lower drug doses than those required for anaesthetic induction, a phenomenon observed across very different species, from invertebrates to mammals. However, the brain is also subject to another form of inertia, familiar to most people: sleep inertia, the feeling of grogginess, confusion and impaired performance that typically follows awakening. Here, we propose a novel account of neural inertia, as the result of sleep inertia taking place after the artificial sleep induced by anaesthetics. We argue that the orexinergic and noradrenergic systems may be key mechanisms for the control of these transition states, with the orexinergic system exerting a stabilising effect through the noradrenergic system. This effect may be reflected at the macroscale in terms of altered functional anticorrelations between default mode and executive control networks of the human brain. The hypothesised link between neural inertia and sleep inertia could explain why different anaesthetic drugs induce different levels of neural inertia, and why elderly individuals and narcoleptic patients are more susceptible to neural inertia. This novel hypothesis also enables us to generate several empirically testable predictions at both the behavioural and neural levels, with potential implications for clinical practice.
... This model was able to account for rapid and complete transitions between sleep and wakefulness and preventing state instability (15) or the occurrence of mixed hybrid states of vigilance (16). Over the last decade, our knowledge of subcortical brain nuclei that control sleep has expanded steadily, leading to the identification of functional specialization within the sleep-wake controlling network and, in parallel, highlighting a previously underappreciated complexity (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35). ...
... An acknowledged limitation of the approach we used is that we likely targeted a heterogeneous population of neurons, as the hypothalamus harbors many different cell types (35,78). We would like to stress that it remains unclear how fine the spatial resolution should be in stimulation experiments such as ours, to obtain meaningful insights into cerebral substrates of global control of sleep and wakefulness. ...
Article
Full-text available
Significance Our current understanding of how sleep is regulated is based upon the model of sleep homeostasis, which defines a variable called Process S as a measure of sleep need, and a so-called “flip-flop” model of state switching, which builds on a notion of a mutually antagonistic relationship between subcortical sleep-promoting and wake-promoting circuits. The neurobiological substrates of the interaction between the sleep switch and Process S are unknown. Our study identifies a previously unrecognized role of hypothalamic circuitry in tuning within-state brain activity or levels of arousal, which in turn determine the homeostatic drive for sleep.
... A virus pseudotyped with the ligand of TVA, EnvA, is injected into the brain region of interest and infects neurons that express TVA during the injection window. This virus can carry fluorescent proteins to label the active neurons, or chemogenetic or optogenetic effector molecules to enable subsequent activation or inhibition of this tagged population (Sakurai et al., 2016;Jiang-Xie et al., 2019). Though not in the POA, this technique identified a population of anesthetic-activated neurons in the neighboring supraoptic nucleus that promote NREM sleep when reactivated at a later time (Jiang-Xie et al., 2019), highlighting the power of this technique in investigations of the shared circuitry hypothesis in the POA and other regions. ...
... This virus can carry fluorescent proteins to label the active neurons, or chemogenetic or optogenetic effector molecules to enable subsequent activation or inhibition of this tagged population (Sakurai et al., 2016;Jiang-Xie et al., 2019). Though not in the POA, this technique identified a population of anesthetic-activated neurons in the neighboring supraoptic nucleus that promote NREM sleep when reactivated at a later time (Jiang-Xie et al., 2019), highlighting the power of this technique in investigations of the shared circuitry hypothesis in the POA and other regions. ...
Article
Full-text available
The role of the hypothalamic preoptic area (POA) in arousal state regulation has been studied since Constantin von Economo first recognized its importance in the early twentieth century. Over the intervening decades, the POA has been shown to modulate arousal in both natural (sleep and wake) as well as drug-induced (anesthetic-induced unconsciousness) states. While the POA is well known for its role in sleep promotion, populations of wake-promoting neurons within the region have also been identified. However, the complexity and molecular heterogeneity of the POA has made distinguishing these two populations difficult. Though multiple lines of evidence demonstrate that general anesthetics modulate the activity of the POA, the region’s heterogeneity has also made it challenging to determine whether the same neurons involved in sleep/wake regulation also modulate arousal in response to general anesthetics. While a number of studies show that sleep-promoting POA neurons are activated by various anesthetics, recent work suggests this is not universal to all arousal-regulating POA neurons. Technical innovations are making it increasingly possible to classify and distinguish the molecular identities of neurons involved in sleep/wake regulation as well as anesthetic-induced unconsciousness. Here, we review the current understanding of the POA’s role in arousal state regulation of both natural and drug-induced forms of unconsciousness, including its molecular organization and connectivity to other known sleep and wake promoting regions. Further insights into the molecular identities and connectivity of arousal-regulating POA neurons will be critical in fully understanding how this complex region regulates arousal states.
... www.nature.com/scientificreports/ These brain regions align with mammalian literature linking activity in preoptic circuits to hypnotic states of sleep and anesthesia 33,34 , and heightened activity in sensory circuits to emergence from anesthesia 35 . ...
... A challenge for zebrafish models of human inherited disorders is that zebrafish and human brains differ structurally 44 . As such, drawing parallels between zebrafish and human brain activity during different behavioral states requires physiological studies to establish that brain regions are functionally related in the two species 35 . In zebrafish, the ability to image activity in brain-wide neuronal ensembles has helped to address this problem. ...
Article
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Delayed emergence from anesthesia was previously reported in a case study of a child with Glycine Encephalopathy. To investigate the neural basis of this delayed emergence, we developed a zebrafish glial glycine transporter ( glyt1 − / − ) mutant model. We compared locomotor behaviors; dose–response curves for tricaine, ketamine, and 2,6-diisopropylphenol (propofol); time to emergence from these anesthetics; and time to emergence from propofol after craniotomy in glyt1−/− mutants and their siblings. To identify differentially active brain regions in glyt1−/− mutants, we used pERK immunohistochemistry as a proxy for brain-wide neuronal activity. We show that glyt1−/− mutants initiated normal bouts of movement less frequently indicating lethargy-like behaviors. Despite similar anesthesia dose–response curves, glyt1−/− mutants took over twice as long as their siblings to emerge from ketamine or propofol, mimicking findings from the human case study. Reducing glycine levels rescued timely emergence in glyt1−/− mutants, pointing to a causal role for elevated glycine. Brain-wide pERK staining showed elevated activity in hypnotic brain regions in glyt1−/− mutants under baseline conditions and a delay in sensorimotor integration during emergence from anesthesia. Our study links elevated activity in preoptic brain regions and reduced sensorimotor integration to lethargy-like behaviors and delayed emergence from propofol in glyt1−/− mutants.
... The γ-aminobutyric acid (GABA) type A (GABA A ) receptor is thought to be a principal cellular target for many anesthetic drugs [3]. GABA A receptor is the major contributor to neuronal inhibition and is widely expressed throughout the brain regions [4]. With decades of scientific efforts, it has been proven that many anesthetic drugs potentiate GABA-induced Cl − current and can directly activate the GABA A receptor at higher dose [1]. ...
Article
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Propofol is widely used for the induction and maintenance of anesthesia, which causes a rapid loss of consciousness. However, the mechanisms underlying the hypnosis effect of propofol are still not fully understood. The thalamic reticular nucleus (TRN) is crucial for regulating wakefulness, sleep rhythm generation, and sleep stability, while the role of TRN in the process of propofol-induced anesthesia is still unknown. Here, we investigated the function of the anterior TRN in propofol general anesthesia. Our results demonstrated that the neural activity of anterior TRN is suppressed during propofol anesthesia, whereas it is robustly activated from anesthesia by recording the calcium signals using fiber photometry technology. The results showed that the activation of anterior TRN neurons by chemogenetic and optogenetic methods shortens the emergency time without changing the induction time. Conversely, chemogenetic or optogenetic inhibition of the TRN neurons leads to a delay in the recovery time. Our study showed that anterior TRN is crucial for behavioral arousal without affecting the induction time of propofol anesthesia.
... In this study, medial prefrontal cortex (MPFC), hippocampus, striatum, and hypothalamus were chosen as targets of the analysis, as these parts were frequently used for evaluating the effects of volatile anesthetics [12][13][14][15]. Differently expressed genes (DEGs) and enriched gene groups were compared between the four parts of the brain and we applied the same analysis to the transcriptome array data of sleeping mice to identify specific gene expression changes in brains exposed to sevoflurane. ...
Article
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Backgrounds Sevoflurane is a most frequently used volatile anesthetics, but its molecular mechanisms of action remain unclear. We hypothesized that specific genes play regulatory roles in brain exposed to sevoflurane. Thus, we aimed to evaluate the effects of sevoflurane inhalation and identify potential regulatory genes by RNA-seq analysis. Methods Eight-week old mice were exposed to sevoflurane. RNA from medial prefrontal cortex, striatum, hypothalamus, and hippocampus were analysed using RNA-seq. Differently expressed genes were extracted and their gene ontology terms were analysed using Metascape. These our anesthetized mouse data and the transcriptome array data of the cerebral cortex of sleeping mice were compared. Finally, the activities of transcription factors were evaluated using a weighted parametric gene set analysis (wPGSA). JASPAR was used to confirm the existence of binding motifs in the upstream sequences of the differently expressed genes. Results The gene ontology term enrichment analysis result suggests that sevoflurane inhalation upregulated angiogenesis and downregulated neural differentiation in each region of brain. The comparison with the brains of sleeping mice showed that the gene expression changes were specific to anesthetized mice. Focusing on individual genes, sevoflurane induced Klf4 upregulation in all sampled parts of brain. wPGSA supported the function of KLF4 as a transcription factor, and KLF4-binding motifs were present in many regulatory regions of the differentially expressed genes. Conclusions Klf4 was upregulated by sevoflurane inhalation in the mouse brain. The roles of KLF4 might be key to elucidating the mechanisms of sevoflurane induced functional modification in the brain.
... 36 These results support the shared circuitry hypothesis of anesthetic hypnosis, which posits that anesthetics exert their hypnotic effects in part by acting on endogenous sleep-wake neuronal circuitry and that independent modulation of the same neurons in these circuits affects the anesthetic state. Within the hypothalamus specifically, anesthetics are known to activate the VLPO, the medial preoptic area, and the supraoptic nucleus, three sleep-promoting nuclei, 17,20,65 and inhibit the wake-stabilizing orexinergic neurons in the lateral hypothalamus. 36,66 However, recent work showing that GABAergic or glutamatergic POA neurons that modulate sleep and wake have no effect on isoflurane induction and recovery time suggests that not all sleep or arousal-promoting neurons play a meaningful role in anesthetic hypnosis. ...
Article
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Endogenous sleep and general anesthesia are distinct states that share similar traits. Of particular interest to neuroscience is the loss of consciousness that accompanies both states. Multiple lines of evidence demonstrate that general anesthetics can co-opt the neural circuits regulating arousal to produce unconsciousness. However, controversy remains as to whether the neural circuits and, more specifically, the same neurons shaping sleep and wakefulness actually do influence the anesthetic state in vivo. Hypothalamic preoptic area (POA) neurons are intimately involved in modulating spontaneous and anesthetic-induced changes in arousal. Nevertheless, recent work suggests that POA GABAergic or glutamatergic neurons capable of regulating endogenous sleep fail to influence the onset or dissipation of anesthesia. We hypothesized that the POA’s broad neuronal diversity could mask convergent roles of a subset of neurons in regulating both arousal and anesthesia. Contrary to a previously published report, we show that chemogenetic activation of POA Tac1 neurons obliterates both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, strongly consolidating the waking state for hours, even during a period of elevated sleep drive. Moreover, chemogenetic activation of Tac1 POA neurons stabilizes the wake state against both isoflurane- and sevoflurane-induced unconsciousness. Tac1-activated mice display a partial resistance to entering isoflurane anesthesia and a more pronounced ability to exit both isoflurane- and sevoflurane-induced unconscious states. We conclude that POA Tac1 neurons can potently reinforce arousal both against endogenous and drug-induced unconscious states. POA Tac1 neurons thus add causal support for the involvement of arousal-regulating systems in the state of general anesthesia.
... Moreover, this doublecontrol mechanism appears to permanently tag the majority of activated cells, leading to high efficiency. The use of lenti and rabiviruses allows the labeling of two or more ensembles in the same brain region and also trans-synaptic tracing of activated cells (Sakurai et al., 2016;Rodriguez et al., 2017;Jiang-Xie et al., 2019;Tschida et al., 2019). CANE is an excellent technology, able to reconstruct efferent and afferent connections, but it cannot be used for whole-brain labeling because viral infection is limited to the injection site. ...
Article
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Visualizing neuronal activation on a brain-wide scale yet with cellular resolution is a fundamental technical challenge for neuroscience. This would enable analyzing how different neuronal circuits are disrupted in pathology and how they could be rescued by pharmacological treatments. Although this goal would have appeared visionary a decade ago, recent technological advances make it eventually feasible. Here, we review the latest developments in the fields of genetics, sample preparation, imaging, and image analysis that could be combined to afford whole-brain cell-resolution activation mapping. We show how the different biochemical and optical methods have been coupled to study neuronal circuits at different spatial and temporal scales, and with cell-type specificity. The inventory of techniques presented here could be useful to find the tools best suited for a specific experiment. We envision that in the next years, mapping of neuronal activation could become routine in many laboratories, allowing dissecting the neuronal counterpart of behavior.
... Dexmedetomidine, in contrast, is a highly specific α2-adrenergic agonist. Its activation of adrenergic receptors is believed to produce sedative effects by inhibiting the release of norepinephrine, which then disinhibits downstream GABAergic neurons in the ventrolateral preoptic nucleus of the hypothalamus (Olkkola and Ahonen, 2008), or other recently identified anesthesia-inducing cell populations (Sukhotinsky et al., 2016;Jiang-Xie et al., 2019), resulting in sedation. A similar circuit involving noradrenergic inhibition of GABAergic interneurons is present in the DG as well (Harley, 2007) and could potentially drive changes in cell proliferation. ...
Article
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In animal studies, prolonged sedation with general anesthetics has resulted in cognitive impairments that can last for days to weeks after exposure. One mechanism by which anesthesia may impair cognition is by decreasing adult hippocampal neurogenesis. Several studies have seen a reduction in cell survival after anesthesia in rodents with most studies focusing on two particularly vulnerable age windows: the neonatal period and old age. However, the extent to which sedation affects neurogenesis in young adults remains unclear. Adult neurogenesis in the dentate gyrus (DG) was analyzed in male and female rats 24 h after a 4-h period of sedation with isoflurane, propofol, midazolam, or dexmedetomidine. Three different cell populations were quantified: cells that were 1 week or 1 month old, labeled with the permanent birthdate markers EdU or BrdU, respectively, and precursor cells, identified by their expression of the endogenous dividing cell marker proliferating cell nuclear antigen (PCNA) at the time of sacrifice. Midazolam and dexmedetomidine reduced cell proliferation in the adult DG in both sexes but had no effect on postmitotic cells. Propofol reduced the number of relatively mature, 28-day old, neurons specifically in female rats and had no effects on younger cells. Isoflurane had no detectable effects on any of the cell populations examined. These findings show no general effect of sedation on adult-born neurons but demonstrate that certain sedatives do have drug-specific and sex-specific effects. The impacts observed on different cell populations predict that any cognitive effects of these sedatives would likely occur at different times, with propofol producing a rapid but short-lived impairment and midazolam and dexmedetomidine altering cognition after a several week delay. Taken together, these studies lend support to the hypothesis that decreased neurogenesis in the young adult DG may mediate the effects of sedation on cognitive function.
... As shown in Fig. 1D, 1.5% and 3% sevoflurane significantly suppressed the calcium signal and induced loss of consciousness (LOC). Transitions into sevoflurane-induced LOC were determined by the changes of EEG pattern from low-voltage fast to high-voltage slow activity and EMG pattern from highly active to completely absent (Jiang-Xie et al., 2019;Pal et al., 2018). It took about 100 s for 3% sevoflurane and 200 s for 1.5% sevoflurane to induce LOC. ...
Article
Despite persistent clinical use for over 170 years, the neuronal mechanisms by which general anesthetics produce hypnosis remain unclear. Previous studies suggest that anesthetics exert hypnotic effects by acting on endogenous arousal circuits. Recently, it has been shown that the medial parabrachial nucleus (MPB) is a novel wake-promoting component in the dorsolateral pons. However, it is not known whether and how the MPB contributes to anesthetic-induced hypnosis. Here, we investigated the action of sevoflurane, a widely used volatile anesthetic agent that best represents the drug class of halogenated ethers, on MPB neurons in mice. Using in vivo fiber photometry, we found that the population activities of MPB neurons were inhibited during sevoflurane-induced loss of consciousness. Using in vitro whole-cell patch-clamp recordings, we revealed that sevoflurane suppressed the firing rate of MPB neurons in concentration-dependent and reversible manners. At a concentration equal to MAC of hypnosis, sevoflurane potentiated synaptic GABAA receptors (GABAA-Rs), and the inhibitory effect of sevoflurane on the firing rate of MPB neurons was completely abolished by picrotoxin, which is a selective GABAA-R antagonist. At a concentration equivalent to MAC of immobility, sevoflurane directly hyperpolarized MPB neurons and induced a significant decrease in membrane input resistance by increasing a basal potassium conductance. Moreover, pharmacological blockade of GABAA-Rs in the MPB prolongs induction and shortens emergence under sevoflurane inhalation at MAC of hypnosis. These results indicate that sevoflurane inhibits MPB neurons through postsynaptic GABAA-Rs and background potassium channels, which contributes to sevoflurane-induced hypnosis.
... It was recently discovered in Fan Wang's lab at Duke that general anesthesia activates firing neurons in the supraoptic nucleus of the hypothalamus (Jiang-Xie et al., 2019). This small nucleus has long projections to the pituitary gland that lead to the release of vasopressin and other hormones into the bloodstream. ...
... Although GABA and galanin are sometimes used as markers for the VLPO (Sherin et al., 1998;Gaus et al., 2002), GABAergic neurons are distributed throughout the POA, and galanin is expressed abundantly in the medial MPOA but only sparsely in the VLPO regions (Figure 2). At the caudal end of the POA, galanin expression is sharply reduced and is restricted to the supraoptic nucleus (SON), which is caudally adjacent to the VLPO and induces sleep (Jiang-Xie et al., 2019). We have examined the expression of many genes and proteins in the POA but have not found any suitable marker for the VLPO. ...
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The preoptic area (POA) has long been recognized as a sleep center, first proposed by von Economo. The POA, especially the medial POA (MPOA), is also involved in the regulation of various innate functions such as sexual and parental behaviors. Consistent with its many roles, the MPOA is composed of subregions that are identified by different gene and protein expressions. This review addresses the current understanding of the molecular and cellular architecture of POA neurons in relation to sleep and reproductive behavior. Optogenetic and pharmacogenetic studies have revealed a diverse group of neurons within the POA that exhibit different neural activity patterns depending on vigilance states and whose activity can enhance or suppress wake, non-rapid eye movement (NREM) sleep, or rapid eye movement (REM) sleep. These sleep-regulating neurons are not restricted to the ventrolateral POA (VLPO) region but are widespread in the lateral MPOA and LPOA as well. Neurons expressing galanin also express gonadal steroid receptors and regulate motivational aspects of reproductive behaviors. Moxd1, a novel marker of sexually dimorphic nuclei (SDN), visualizes the SDN of the POA (SDN-POA). The role of the POA in sleep and other innate behaviors has been addressed separately; more integrated observation will be necessary to obtain physiologically relevant insight that penetrates the different dimensions of animal behavior.
... Sleep is a natural form of unconsciousness and is required for memory consolidation, including hippocampus-dependent memories [49,56]. Recent work suggested that sleep-and anesthesia-promoting circuits differ [92,93] while others identified circuit elements shared between sleep and general anesthesia [94], especially during development [58]. Therefore, we asked how the diverse alterations of CA1 network dynamics imposed by the different anesthetics impact memory consolidation. ...
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General anesthesia is characterized by reversible loss of consciousness accompanied by transient amnesia. Yet, long-term memory impairment is an undesirable side effect. How different types of general anesthetics (GAs) affect the hippocampus, a brain region central to memory formation and consolidation, is poorly understood. Using extracellular recordings, chronic 2-photon imaging, and behavioral analysis, we monitor the effects of isoflurane (Iso), medetomidine/midazolam/fentanyl (MMF), and ketamine/xylazine (Keta/Xyl) on network activity and structural spine dynamics in the hippocampal CA1 area of adult mice. GAs robustly reduced spiking activity, decorrelated cellular ensembles, albeit with distinct activity signatures, and altered spine dynamics. CA1 network activity under all 3 anesthetics was different to natural sleep. Iso anesthesia most closely resembled unperturbed activity during wakefulness and sleep, and network alterations recovered more readily than with Keta/Xyl and MMF. Correspondingly, memory consolidation was impaired after exposure to Keta/Xyl and MMF, but not Iso. Thus, different anesthetics distinctly alter hippocampal network dynamics, synaptic connectivity, and memory consolidation, with implications for GA strategy appraisal in animal research and clinical settings.
... Intriguingly, chemogenetic activation of SON AVP neurons, another source of ADH, has been demonstrated to promote sleep. 63 Thus, the hypnotic effect of SON AVP neurons might cancel the arousal effect of PVH AVP neurons upon water deprivation. Although PVH AVP neurons and SON AVP neurons have been considered redundant pathways in body-fluid homeostasis, recent studies suggested that these two groups of AVP neurons may be involved in different physiological behaviors and receive afferent inputs from different combinations of brain regions. ...
Article
The sleep-wakefulness cycle is regulated by complicated neural networks that include many different populations of neurons throughout the brain. Arginine vasopressin neurons in the paraventricular nucleus of the hypothalamus (PVH AVP) regulate various physiological events and behaviors, such as body-fluid homeostasis, blood pressure, stress response, social interaction, and feeding. Changes in arousal level often accompany these PVH AVP-mediated adaptive responses. However, the contribution of PVH AVP neurons to sleep-wakefulness regulation has remained unknown. Here, we report the involvement of PVH AVP neurons in arousal promotion. Optogenetic stimulation of PVH AVP neurons rapidly induced transitions to wakefulness from both NREM and REM sleep. This arousal effect was dependent on AVP expression in these neurons. Similarly, chemogenetic activation of PVH AVP neurons increased wakefulness and reduced NREM and REM sleep, whereas chemogenetic inhibition of these neurons significantly reduced wakefulness and increased NREM sleep. We observed dense projections of PVHAVP neurons in the lateral hypothalamus with potential connections to orexin/hypocretin (LHOrx) neurons. Optogenetic stimulation of PVHAVP neuronal fibers in the LH immediately induced wakefulness, whereas blocking orexin receptors attenuated the arousal effect of PVH AVP neuronal activation drastically. Monosynaptic rabies-virus tracing revealed that PVH AVP neurons receive inputs from multiple brain regions involved in sleep-wakefulness regulation, as well as those involved in stress response and energy metabolism. Moreover, PVH AVP neurons mediated the arousal induced by novelty stress and a melanocortin receptor agonist melanotan-II. Thus, our data suggested that PVH AVP neurons promote wakefulness via LH Orx neurons in the basal sleep-wakefulness and some stressful conditions.
... However, these state transitions affect firing rate differently across brain regions. In sleep-promoting brain areas such as the supraoptic nucleus in the hypothalamus, MFRs are increased during sleep [37]. In some but not all circuits of the neocortex and hippocampus, MFRs decrease during sleep but return to apparent state-dependent set points following transitions into higher vigilance states [38][39][40]. ...
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Neural circuit functions are stabilized by homeostatic processes at long timescales in response to changes in behavioral states, experience, and learning. However, it remains unclear which specific physiological variables are being stabilized and which cellular or neural network components compose the homeostatic machinery. At this point, most evidence suggests that the distribution of firing rates among neurons in a neuronal circuit is the key variable that is maintained around a set-point value in a process called 'firing rate homeostasis.' Here, we review recent findings that implicate mitochondria as central players in mediating firing rate homeostasis. While mitochondria are known to regulate neuronal variables such as synaptic vesicle release or intracellular calcium concentration, the mitochondrial signaling pathways that are essential for firing rate homeostasis remain largely unknown. We used basic concepts of control theory to build a framework for classifying possible components of the homeostatic machinery that stabilizes firing rate, and we particularly emphasize the potential role of sleep and wakefulness in this homeostatic process. This framework may facilitate the identification of new homeostatic pathways whose malfunctions drive instability of neural circuits in distinct brain disorders.
... This experiment revealed three clusters of Fos + neurons under isoflurane but not oxygen: one in the CeA, one in the oval division of the bed nucleus of the stria terminalis (ovBNST) and one in the supraoptic nucleus (SON) (Fig. 1a and Extended Data Fig. 1a-c). We recently showed that the GA-activated SON neurons promote slow-wave sleep and extend GA duration (i.e this cluster of cells is related to the sedative aspects of GA) 7 . The functions of GA-activated ovBNST neurons are not yet known. ...
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General anesthesia (GA) can produce analgesia (loss of pain) independent of inducing loss of consciousness, but the underlying mechanisms remain unclear. We hypothesized that GA suppresses pain in part by activating supraspinal analgesic circuits. We discovered a distinct population of GABAergic neurons activated by GA in the mouse central amygdala (CeAGA neurons). In vivo calcium imaging revealed that different GA drugs activate a shared ensemble of CeAGA neurons. CeAGA neurons also possess basal activity that mostly reflects animals’ internal state rather than external stimuli. Optogenetic activation of CeAGA potently suppressed both pain-elicited reflexive and self-recuperating behaviors across sensory modalities and abolished neuropathic pain-induced mechanical (hyper-)sensitivity. Conversely, inhibition of CeAGA activity exacerbated pain, produced strong aversion and canceled the analgesic effect of low-dose ketamine. CeAGA neurons have widespread inhibitory projections to many affective pain-processing centers. Our study points to CeAGA as a potential powerful therapeutic target for alleviating chronic pain. Hua and Chen et al. show that general anesthesia activates a distinct population of central amygdala neurons and that these neurons can potently suppress pain responses through their widespread projections to many pain-processing centers in the brain.
... First and foremost, anesthesia co-opts endogenous sleep-related circuits by recruiting sleep-promoting nuclei such as the lateral habenula and the ventrolateral preoptic area, and by simultaneously suppressing arousal-promoting nuclei such as the tuberomammillary nucleus and the dorsal raphe [9,45,46]. More recently, it has been demonstrated that the optogenetic reactivation of a population of neuroendocrine anesthesia-activated neurons in the supraoptic nucleus promoted slow-wave sleep, and that ablation of these same cells conversely led to a significant loss of both slow-wave and REM sleep, and a shorter duration of general anesthesia [47]. Furthermore, sleep and anesthesia have a reciprocal influence on one another; sleep deprivation affects both the induction and recovery from anesthesia [48], and sleep debt induced by sleep deprivation can be attenuated by specific anesthetics [49,50]. ...
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Anesthesia is a powerful tool in neuroscientific research, especially in sleep research where it has the experimental advantage of allowing surgical interventions that are ethically problematic in natural sleep. Yet, while it is well documented that different anesthetic agents produce a variety of brain states, and consequently have differential effects on a multitude of neurophysiological factors, these outcomes vary based on dosages, the animal species used, and the pharmacological mechanisms specific to each anesthetic agent. Thus, our aim was to conduct a controlled comparison of spontaneous electrophysiological dynamics at a surgical plane of anesthesia under six common research anesthetics using a ubiquitous animal model, the Sprague-Dawley rat. From this direct comparison, we also evaluated which anesthetic agents may serve as pharmacological proxies for the electrophysiological features and dynamics of unconscious states such as sleep and coma. We found that at a surgical plane, pentobarbital, isoflurane and propofol all produced a continuous pattern of burst-suppression activity, which is a neurophysiological state characteristically observed during coma. In contrast, ketamine-xylazine produced synchronized, slow-oscillatory activity, similar to that observed during slow-wave sleep. Notably, both urethane and chloral hydrate produced the spontaneous, cyclical alternations between forebrain activation (REM-like) and deactivation (non-REM-like) that are similar to those observed during natural sleep. Thus, choice of anesthesia, in conjunction with continuous brain state monitoring, are critical considerations in order to avoid brain-state confounds when conducting neurophysiological experiments.
... Indeed, the more recent data pinpoints the involvement of far complex structural and molecular processes and mechanisms, and extended neural circuits in the induction of the state of transient coma, including changes in the activity of hypothalamic, midbrain, and brain stem modulator networks (Brown et al. 2010;Ching and Brown 2014). Although the recent demonstration of reversible activation of a selected group of neuroendocrine neurons in the supra-optic area by several general anesthetics (Jiang-Xie et al. 2019) offers a unifying framework for a common neural substrate for the effects of general anesthetics, it leaves unanswered a wide range of questions over their transient or lasting actions on structure and functions of cortical and hippocampal neurons, including changes in dynamics and plasticity of dendritic spines, with long-lasting neurocognitive and behavioral impact. Notwithstanding the multiplicity of primary targets and action mechanisms, general anesthetics seem to converge on a few shared processes which in one way or another destabilize dendritic spines and stimulate synaptic remodeling (Fig. 3). ...
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Ever since its first use in surgery, general anesthesia has been regarded as a medical miracle enabling countless life-saving diagnostic and therapeutic interventions without pain sensation and traumatic memories. Despite several decades of research, there is a lack of understanding of how general anesthetics induce a reversible coma-like state. Emerging evidence suggests that even brief exposure to general anesthesia may have a lasting impact on mature and especially developing brains. Commonly used anesthetics have been shown to destabilize dendritic spines and induce an enhanced plasticity state, with effects on cognition, motor functions, mood, and social behavior. Herein, we review the effects of the most widely used general anesthetics on dendritic spine dynamics and discuss functional and molecular correlates with action mechanisms. We consider the impact of neurodevelopment, anatomical location of neurons, and their neurochemical profile on neuroplasticity induction, and review the putative signaling pathways. It emerges that in addition to possible adverse effects, the stimulation of synaptic remodeling with the formation of new connections by general anesthetics may present tremendous opportunities for translational research and neurorehabilitation.
... CCX/A743 and Table S3, http://links.lww.com/CCX/ A746) are consistent with recent findings suggesting a common pathway for the action of various sedatives/ anesthetics (38). ...
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Evaluation of sleep quality in critically ill patients is difficult using conventional scoring criteria. The aim of this study was to examine sleep in critically ill patients with and without light sedation using the odds ratio product, a validated continuous metric of sleep depth (0 = deep sleep; 2.5 = full wakefulness) that does not rely on the features needed for conventional staging. Retrospective study. A 16-bed medical-surgical ICU. Twenty-three mechanically ventilated patients who had previously undergone two nocturnal sleep studies, one without and one with sedation (propofol, n = 12; dexmedetomidine, n = 11). None. Sleep architecture was evaluated with odds ratio product analysis by the distribution of 30-second epochs with different odds ratio product values. Electroencephalogram spectral patterns and frequency of wake intrusions (3-s odds ratio product > 1.75) were measured at different odds ratio product levels. Thirty-seven normal sleepers were used as controls. Compared with normal sleepers, unsedated critically ill patients spent little time in stable sleep (percent odds ratio product < 1.0: 31% vs 63%; p < 0.001), whereas most of the time were either in stage wake (odds ratio product > 1.75) or in a transitional state (odds ratio product 1.0–1.75), characterized by frequent wake intrusions. Propofol and dexmedetomidine had comparable effects on sleep. Sedation resulted in significant shift in odds ratio product distribution toward normal; percent odds ratio product less than 1.0 increased by 54% (p = 0.006), and percent odds ratio product greater than 1.75 decreased by 48% (p = 0.013). In six patients (26%), sedation failed to improve sleep. In stable critically ill unsedated patients, sleep quality is poor with frequent wake intrusions and little stable sleep. Light sedation with propofol or dexmedetomidine resulted in a shift in sleep architecture toward normal in most, but not all, patients.
... Its purpose is to deprive senses to prevent a motor response to stimuli and induce amnesia. 32 Two kinds of general anesthetics are widely used: halogenated gases (for example, halothane, desflurane, isoflurane, and sevoflurane) and intravenous anesthetics (for example ketamine, opioids, etomidate, and propofol). Most general anesthetics act on γaminobutyric acid (GABA) A receptors, and their mechanism and location of action in GABAergic transmission differ. ...
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Bijia Song, Junchao Zhu Department of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, Liaoning, People’s Republic of ChinaCorrespondence: Junchao ZhuDepartment of Anesthesiology, Shengjing Hospital of China Medical University, Shenyang, Liaoning, People’s Republic of ChinaEmail zhujunchao1@hotmail.comAbstract: Perioperative sleep disturbances are commonly observed before, during, and after surgery and can be caused by several factors, such as preoperative negative moods, general anesthetics, surgery trauma, and pain. Over the past decade, the fast-acting antidepressant effects of the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine represent one of the most attractive discoveries in the field of psychiatry, such as antidepressant and anxiolytic effects. It is also widely used as a short-acting anesthetic and analgesic. Recent research has revealed new possible applications for ketamine, such as for perioperative sleep disorders and circadian rhythm disorders. Here, we summarize the risk factors for perioperative sleep disturbances, outcomes of perioperative sleep disturbances, and mechanism of action of ketamine in improving perioperative sleep quality.Keywords: perioperative sleep disturbances, ketamine, antidepressant, anxiolytic, anti-inflammation
... Brain slices can be maintained for weeks in organotypic culture to investigate long-term changes associated with anesthetic exposure models (Drexler et al., 2010), which provide a valuable model for analyzing long-term anesthetic effects on synaptic plasticity. This method has enabled site-specific pharmacologic investigations of synaptic modulation (Joksovic et al., 2015;Rodgers et al., 2015), as well as optogenetic (Murphy et al., 2020) and chemogenetic (Jiang-Xie et al., 2019) studies of anesthetic action, all of which hold promise to help delineate cell-type specific and circuit-level pharmacology. However, this system has its own limitations and technical variations that must be considered when comparing data (Humpel, 2015). ...
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General anesthetics disrupt brain processes involved in consciousness by altering synaptic patterns of excitation and inhibition. In the cerebral cortex and hippocampus, GABAergic inhibition is largely mediated by inhibitory interneurons, a heterogeneous group of specialized neuronal subtypes that form characteristic microcircuits with excitatory neurons. Distinct interneuron subtypes regulate specific excitatory neuron networks during normal behavior, but how these interneuron subtypes are affected by general anesthetics is unclear. This narrative review summarizes current principles of the synaptic architecture of cortical and interneuron subtypes, their contributions to different forms of inhibition, and their roles in distinct neuronal microcircuits. The molecular and cellular targets in these circuits that are sensitive to anesthetics are reviewed in the context of how anesthetics impact interneuron function in a subtype-specific manner. The implications of this functional interneuron diversity for mechanisms of anesthesia are discussed, as are their implications for anesthetic-induced changes in neural plasticity and overall brain function.
... The generated NO stimulates sGC, converting GTP to cGMP that activates protein kinase (PKG), resulting in penile erection. Also, it is likely that glutamine is converted to glutamate [42], which acts via the N-methyl-D-aspartate receptor (NMDA receptor) to induce excitatory action [76], thus inhibiting SD-induced male sexual dysfunction and facilitating male sexual locomotory activities. ...
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Oxidative stress has been linked with sleep deprivation (SD)-induced pathological conditions and reproductive dysfunction. On the other hand, glutamine has been established to have antioxidant property. However, the impact of SD, with or without glutamine, on male reproductive function is yet to be elucidated. Thus, this study was designed to investigate the role of SD, with or without glutamine, on male reproductive function and possible associated mechanisms. Ten-week old male Wistar rats weighing 175.6 g± 0.42 were randomly assigned into vehicle that received per os (p.o.) distilled water, glutamine (1 g/kg; po), SD, and SD + glutamine that received treatments as glutamine and SD. Treatment/exposure lasted for 72 h. The results showed that SD led to reduced body weight, seminiferous luminal and epididymal sperm density, low sperm quality, increased testicular and epididymal malondialdehyde, uric acid, DNA fragmentation, and testicular injury markers. In addition, SD caused a reduction in reduced glutathione level and activities of superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, and glutathione-S-transferase. Also, SD increased tumor necrotic factor-α, interleukin-1β, and nuclear factor-kappa B levels. Furthermore SD led to impaired libido and erectile dysfunction, and suppression of circulatory nitric oxide, gonadotropins and testosterone, and penile cGMP. However, glutamine attenuated the effects induced by SD. Taken together, the findings of this study demonstrate that SD induces reproductive dysfunction via glutathione-dependent defense depletion and down-regulation of NO/cGMP signaling, which was abolished by glutamine supplementation.
... 21, 22 However, common anesthetic substrates in the brain exist, such as the activation of hypothalamic neurons. 23 Here, we will focus our discussion on studies that use propofol, sevoflurane, or isoflurane for maintenance of general anesthesia, since they form much of the literature investigating mesolimbic circuitry in emergence. Further mechanistic basic science research is needed to examine whether findings hold true across disparate anesthetic conditions. ...
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Increasing evidence supports a role for brain reward circuitry in modulating arousal along with emergence from anesthesia. Emergence remains an important frontier for investigation, since no drug exists in clinical practice to initiate rapid and smooth emergence. This review discusses clinical and preclinical evidence indicating a role for two brain regions classically considered integral components of the mesolimbic brain reward circuitry, the ventral tegmental area and the nucleus accumbens, in emergence from propofol and volatile anesthesia. Then there is a description of modern systems neuroscience approaches to neural circuit investigations that will help span the large gap between preclinical and clinical investigation with the shared aim of developing therapies to promote rapid emergence without agitation or delirium. This article proposes that neuroscientists include models of whole-brain network activity in future studies to inform the translational value of preclinical investigations and foster productive dialogues with clinician anesthesiologists.
Article
The Wistar audiogenic rat (WAR) strain is used as an animal model of epilepsy, which when submitted to acute acoustic stimulus presents tonic‐clonic seizures, mainly dependent on brainstem (mesencephalic) structures. However, when WARs are exposed to chronic acoustic stimuli (audiogenic kindling–AK), they usually present tonic‐clonic seizures, followed by limbic seizures, after recruitment of forebrain structures such as the cortex, hippocampus and amygdala. Although some studies have reported that hypothalamic‐hypophysis function is also altered in WAR through modulating vasopressin (AVP) and oxytocin (OXT) secretion, the role of these neuropeptides in epilepsy still is controversial. We analyzed the impact of AK and consequent activation of mesencephalic neurocircuits and the recruitment of forebrain limbic (LiR) sites on the hypothalamic‐neurohypophysial system and expression of Avpr1a and Oxtr in these structures. At the end of the AK protocol, nine out of 18 WARs presented LiR. Increases in both plasma vasopressin and oxytocin levels were observed in WAR when compared to Wistar rats. These results were correlated with an increase in the expressions of heteronuclear (hn) and messenger (m) RNA for Oxt in the paraventricular nucleus (PVN) in WARs submitted to AK that presented LiR. In the paraventricular nucleus, the hnAvp and mAvp expressions increased in WARs with and without LiR, respectively. There were no significant differences in Avp and Oxt expression in supraoptic nuclei (SON). Also, there was a reduction in the Avpr1a expression in the central nucleus of the amygdala and frontal lobe in the WAR strain. In the inferior colliculus, Avpr1a expression was lower in WARs after AK, especially those without LiR. Our results indicate that both AK and LiR in WARs lead to changes in the hypothalamic‐neurohypophysial system and its receptors, providing a new molecular basis to better understaind epilepsy.
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General anesthetics during surgery are presumed to block pain by dampening brain activity and promoting loss-of-consciousness. A new study shows that anesthetics activate an endogenous analgesia neural ensemble in the central nucleus of the amygdala.
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We review evidence challenging the hypothesis that memories are processed or consolidated in sleep. We argue that the brain is in an unconscious state in sleep, akin to general anesthesia, and hence is incapable of meaningful cognitive processing – the sole purview of waking consciousness. At minimum, the encoding of memories in sleep would require that waking events are faithfully transferred to and reproduced in sleep. Remarkably, however, this has never been demonstrated, as waking experiences are never truly replicated in sleep but rather appear in very altered or distorted forms. General anesthetics (GAs) exert their effects through endogenous sleep‐wake control systems and accordingly GAs and sleep share several common features: sensory blockade, immobility, amnesia and lack of awareness (unconsciousness). The loss of consciousness in non‐REM (NREM) sleep or to GAs is characterized by: (1) delta oscillations throughout the cortex; (2) marked reductions in neural activity (from waking) over widespread regions of the cortex, most pronounced in frontal and parietal cortices; and (3) a significant disruption of the functional connectivity of thalamocortical and corticocortical networks, particularly those involved in “higher order” cognitive functions. Several (experimental) reports in animals and humans have shown that disrupting the activity of the cortex, particularly the orbitofrontal cortex, severely impairs higher order cognitive and executive functions. The profound and widespread deactivation of the cortex in the unconscious states of NREM sleep or GA would be expected to produce an equivalent, or undoubtedly a much greater, disruptive effect on mnemonic and cognitive functions. In conclusion, we contend that the unconscious, severely altered state of the brain in NREM sleep would negate any possibility of cognitive processing in NREM sleep. This article is protected by copyright. All rights reserved.
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In light of the general shift from rats to mice as the leading rodent model in neuroscience research we used c-Fos expression as a tool to survey brain regions in the mouse in which neural activity differs between the states of wakefulness and pentobarbital-induced general anesthesia. The aim was to complement prior surveys carried out in rats. In addition to a broad qualitative review, 28 specific regions of interest (ROIs) were evaluated quantitatively. Nearly all ROIs in the cerebral cortex showed suppressed activity. Subcortically, however, some ROIs showed suppression, some showed little change, and some showed increased activity. The overall picture was similar to the rat. Special attention was devoted to ROIs significantly activated during anesthesia as such loci might actively drive the transition to anesthetic unconsciousness rather than responding passively to inhbitory agents distributed globally (the “wet blanket” hypothesis). Twelve such “anesthesia-on” ROIs were identified: the paraventricular hypothalamic nucleus, supraoptic nucleus, tuberomamillary nucleus, lateral habenular nucleus, dentate gyrus, nucleus raphe pallidus, central amygdaloid nucleus, perifornical lateral hypothalamus, ventro-lateral preoptic area, lateral septum, paraventricular thalamic nucleus and zona incerta. The same primary anti-FOS antibody was used in all mice, but two alternative reporter systems were employed: ABC-diaminobenzidine and the currently more popular AlexaFluor488. Fluorescence tagging revealed far fewer FOS-immunoreactive neurons, sounding an alert that the reporter system chosen can have major effects on results obtained.
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One of the greatest unresolved mysteries in medicine relates to the molecular and neuronal mechanisms through which general anesthetics abolish perception. A new study in mice with mutations affecting mitochondrial complex 1 suggests that anesthetic-disruption of cellular energetics impairs endocytosis to alter synaptic function.
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The purpose of this article is to review (1) sleep mechanism under general anesthesia, harmful effects of postoperative sleep disturbances; (2) risk factors associated with postoperative sleep disturbances; (3) measures to prevent and improve postoperative sleep disturbances. General anesthesia changes the postoperative sleep structure especially in elderly patients after major surgery and results in a high incidence rate of sleep disturbances. Sleep disturbances produce harmful effects on postoperative patients and lead to a higher risk of delirium, more cardiovascular events, and poorer recovery. Some researchers do propose non-pharmacological treatments such as attention to environmental and psychological factors, application of electroacupuncture (EA) technology and pharmacological treatments are helpful, but larger high-quality clinical trials with longer following-up are needed to further investigate the efficacy and safety.
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Although general anesthesia is normally induced by systemic dosing, an anesthetic state can be induced in rodents by microinjecting minute quantities of GABAergic agents into the brainstem mesopontine tegmental anesthesia area (MPTA). Correspondingly, lesions to the MPTA render rats relatively insensitive to standard anesthetic doses delivered systemically. Using a chemogenetic approach we have identified and characterized a small subpopulation of neurons restricted to the MPTA which, when excited, render the animal anesthetic by sensorimotor (immobility) and electroencephalographic (EEG) criteria. These “effector-neurons” do not express GABAAδ-Rs, the likely target of GABAergic anesthetics. Rather, we report a distinct sub-population of nearby MPTA neurons which do. During anesthetic induction these likely excite the effector-neurons by disinhibition. Within the effector population ~ 70% appear to be glutamatergic, ~30% GABAergic and ~ 40% glycinergic. Most are projection neurons that send ascending or descending axons to distant targets associated with the individual functional components of general anesthesia: atonia, analgesia, amnesia, and loss-of-consciousness.
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The purpose of this study is to provide input to the leadership of the Indonesian Army National Armed Forces Headquarters regarding the importance of improving Human Resources through increasing good Work Motivation and applicable Competency Strategy order to produce good Organizational Commitment and Organizational Performance to support the success of the National Army Headquarters. Indonesian Army, especially in the General Section of the Indonesian Army National Army The design/design and research method used in this research is hypothesis testing. This research is a quantitative non-experimental, using a questionnaire given to 95 respondents. This research was conducted at the Indonesian Army National Army Headquarters. Data analysis using SPSS and PLS.3.20 software with multivariate Structural Equation Model (SEM) analysis method. The results of this study indicate that: The influence of Strategic Competency, Work Motivation on Organizational Commitment is positive and significant. The effect of Organizational Commitment on Organizational Performance is positive and significant. The effect of Organizational Commitment mediating Strategic Competency, Work Motivation on Organizational Performance is positive and significant. It means that the higher/positive mediation of Organizational Commitment to Strategic Competency, Work Motivation, the higher/positive Organizational Performance. Theoretical implications: Organizational Commitment as a mediating of Strategic Competency, Work Motivation can able to improve Organizational Performance, by increasing Organizational Commitment through increasing its dimensions will be able to improve Organizational Performance of the General Section of the Indonesian National Army, Inspectorate General of the Indonesian Army, National Army Personnel Staff Indonesian Army. Logistics Staff of the Indonesian Army National Army, Planning and Budgeting Staff of the Indonesian Army's National Armed Forces
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General anesthetics induce loss of consciousness, a global change in behavior. However, a corresponding global change in activity in the context of defined cortical cell types has not been identified. Here, we show that spontaneous activity of mouse layer 5 pyramidal neurons, but of no other cortical cell type, becomes consistently synchronized in vivo by different general anesthetics. This heightened neuronal synchrony is aperiodic, present across large distances, and absent in cortical neurons presynaptic to layer 5 pyramidal neurons. During the transition to and from anesthesia, changes in synchrony in layer 5 coincide with the loss and recovery of consciousness. Activity within both apical and basal dendrites is synchronous, but only basal dendrites’ activity is temporally locked to somatic activity. Given that layer 5 is a major cortical output, our results suggest that brain-wide synchrony in layer 5 pyramidal neurons may contribute to the loss of consciousness during general anesthesia.
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Retinal ganglion cells (RGCs), the output neurons of the retina, allow us to perceive our visual environment. RGCs respond to rod/cone input through the retinal circuitry, however, a small population of RGCs are in addition intrinsically photosensitive (ipRGCs) and project to unique targets in the brain to modulate a broad range of subconscious visual behaviors such as pupil constriction and circadian photoentrainment. Despite the discovery of ipRGCs nearly two decades ago, there is still little information about how or if conventional RGCs (non‐ipRGCs) target ipRGC‐recipient nuclei to influence subconscious visual behavior. Using a dual recombinase fluorescent reporter strategy, we showed that conventional RGCs innervate many subconscious ipRGC‐recipient nuclei, apart from the suprachiasmatic nucleus. We revealed previously unrecognized stratification patterns of retinal innervation from ipRGCs and conventional RGCs in the ventral portion of the lateral geniculate nucleus. Further, we found that the percent innervation of ipRGCs and conventional RGCs across ipsi‐ and contralateral nuclei differ. Our data provide a blueprint to understand how conventional RGCs and ipRGCs innervate different brain regions to influence subconscious visual behaviors.
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General anesthetic agents are thought to induce loss-of-consciousness (LOC) and enable pain-free surgery by acting on the endogenous brain circuitry responsible for sleep-wake cycling. In clinical use, the entire CNS is exposed to anesthetic molecules with LOC usually attributed to synaptic suppression in the cerebral cortex and immobility and analgesia to agent action in the spinal cord and brainstem. This model of patch-wise suppression has been challenged, however, by the observation that all functional components of anesthesia can be induced by focal delivery of minute quantities of GABAergic agonists to the brainstem mesopontine tegmental anesthesia area (MPTA). We compared spectral features of the cortical electroencephalogram (EEG) in rats during systemic anesthesia and anesthesia induced by MPTA microinjection. Systemic administration of (GABAergic) pentobarbital yielded the sustained, δ-band dominant EEG signature familiar in clinical anesthesia. In contrast, anesthesia induced by MPTA microinjection (pentobarbital or muscimol) featured epochs of δ-band EEG alternating with the wake-like EEG, the pattern typical of natural non-rapid-eye-movement (NREM) and REM sleep. The rats were not sleeping, however, as they remained immobile, atonic and unresponsive to noxious pinch. Recalling the paradoxical wake-like quality the EEG during REM sleep, we refer to this state as “paradoxical anesthesia”. GABAergic anesthetics appear to co-opt both cortical and spinal components of the sleep network via dedicated axonal pathways driven by MPTA neurons. Direct drug exposure of cortical and spinal neurons is not necessary, and is probably responsible for off-target side-effects of systemic administration including monotonous δ-band EEG, hypothermia and respiratory depression. Significance statement The concept that GABAergic general anesthetic agents induce loss-of-consciousness by substituting for an endogenous neurotransmitter, thereby co-opting neural circuitry responsible for sleep-wake transitions, has gained considerable traction. However, the electroencephalographic (EEG) signatures of sleep and anesthesia differ fundamentally. We show that when the anesthetic state is generated by focal delivery of GABAergics into the mesopontine tegmental anesthesia area (MPTA) the resulting EEG repeatedly transitions between delta-wave-dominant and wake-like patterns much as in REM-NREM sleep. This suggests that systemic (clinical) anesthetic delivery, which indiscriminately floods the entire cerebrum with powerful inhibitory agents, obscures the sleep-like EEG signature associated with the less adulterated form of anesthesia obtained when the drugs are applied selectively to loci where the effective neurotransmitter substitution actually occurs.
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Despite extensive evidence on the organ protective effects of sevoflurane, its effect on disturbed sleep remains unclear. We hypothesised that sevoflurane preconditioning positively impacts disturbed sleep caused by systemic inflammation. A prospective, randomised laboratory investigation was conducted in C57BL/6J mice. A mouse model of lipopolysaccharide (LPS)‐induced systemic inflammation was employed to investigate the effects of sevoflurane on sleep recovery. Symptom recovery was evaluated through electroencephalography/electromyography (EEG/EMG) and histological studies. The mice were exposed to 2% sevoflurane before and after peritoneal injection of LPS. The EEG and EMG were recorded for 24 h after the procedure. Brain tissue was harvested after the sevoflurane/LPS procedure and was immunostained using individual antibodies against choline acetyltransferase (ChAT) and Fos. The ChAT‐positive and ChAT/Fos double‐positive cells were analysed quantitatively in the pedunculopontine tegmental nucleus and laterodorsal tegmental nucleus (PPTg/LDTg). Compared with control mice, mice preconditioned with sevoflurane but not post‐conditioned showed a significant increase in rapid eye movement (REM) sleep during EEG recording following the LPS challenge. They also demonstrated a shorter REM latency, indicating an early recovery from LPS‐altered sleep. The bouts of REM episodes were retained with sevoflurane preconditioning. More ChAT/Fos double‐positive cells were observed in the PPTg/LDTg in the sevoflurane preconditioning plus LPS group than in the LPS‐only group. Sevoflurane preconditioning promotes recovery from altered sleep induced by systemic inflammation. Activation of PPTg/LDTg is considered a mechanism underlying sleep reintegration. The recovery phenomenon shows potential for clinical application in cases of sleep disturbances induced by systemic inflammation.
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We previously reported that brotizolam, but not suvorexant, delayed recovery from isoflurane anesthesia in mice. However, the effects of hypnotics may be altered by the circadian rhythm. Locomotor activity was measured using sighted (ICR and C57BL/6J) and blind (FVB/N and C3H/HeN) mice, and the effects of hypnotics on isoflurane anesthesia were compared during the light and dark periods. In sighted mice, recovery induced by brotizolam was delayed in the light period, while that by suvorexant was delayed in the dark period. In C57BL/6J mice, delayed recovery induced by brotizolam was marked, and that by suvorexant was observed in the light and dark periods. Locomotor activity was low in the last 6 hours of the dark period in blind mice, and was similar to that in the light period. In blind mice, delayed recovery induced by brotizolam was identical in both periods, while suvorexant did not influence recovery from isoflurane anesthesia. These results suggest that the effects of hypnotics on isoflurane anesthesia are altered by the circadian rhythm and that daily light-dark stimuli may be required for the chronopharmacological effects of hypnotics.
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Common human experience is that a long period without sleep is unsustainable, and it is also detrimental to health and behavior. The powerful and primal urge to sleep after sleep deprivation is intense and seems inescapable. The longer we stay awake, the more we feel the need to sleep, and however much we resist, we will inevitably succumb. Although it is obvious what benefits derive from other common and strong physiological drives, such as hunger, sex, and thirst, it is less obvious what drives us to sleep and what benefits accrue. Understanding the biochemical or circuit basis for the sleep drive could enable the benefits of sleep to be artificially stimulated with a new generation of sedative drugs.
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The brain undergoes rapid, dramatic, and reversible transitioning between states of wakefulness and unconsciousness during natural sleep and in pathological conditions such as hypoxia, hypotension, and concussion. Transitioning can also be induced pharmacologically using general anesthetic agents. The effect is selective. Mobility, sensory perception, memory formation, and awareness are lost while numerous housekeeping functions persist. How is selective transitioning accomplished? Classically a handful of brainstem and diencephalic “arousal nuclei” have been implicated in driving brain-state transitions on the grounds that their net activity systematically varies with brain state. Here we used transgenic targeted recombination in active populations mice
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The hypothalamic supraoptic nucleus (SON) is a core osmoregulatory control centre that deciphers information about the metabolic state of the organism and orchestrates appropriate homeostatic (endocrine) and allostatic (behavioural) responses. We have used RNA sequencing to describe the polyadenylated transcriptome of the SON of the male Wistar Han rat. These data have been mined to generate comprehensive catalogues of functional classes of genes (enzymes, transcription factors, endogenous peptides, G protein coupled receptors, transporters, catalytic receptors, channels and other pharmacological targets) expressed in this nucleus in the euhydrated state, and that together form the basal substrate for its physiological interactions. We have gone on to show that fluid deprivation for 3 days (dehydration) results in changes in the expression levels of 2247 RNA transcripts, which have similarly been functionally catalogued, and further mined to describe enriched gene categories and putative regulatory networks (Regulons) that may have physiological importance in SON function related plasticity. We hope that the revelation of these genes, pathways and networks, most of which have no characterised roles in the SON, will encourage the neuroendocrine community to pursue new investigations into the new ‘known-unknowns’ presented in this study.
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Alterations in thalamic GABAergic signaling are implicated in mediating the rise in 12-30Hz electroencephalogram (EEG) activity that signals anesthetic-induced loss-of-consciousness with GABAA receptor-targeting general anesthetics. A number of modeling studies have identified that anesthetic-induced alterations in thalamocortico-corticothalamic signaling in the same network that generates sleep spindles would be sufficient to elicit this key EEG signature of anesthetic hypnosis with general anesthetic agents. Accordingly, we hypothesize that targeted stimulation of this thalamic GABAergic circuitry into a sleep-spindle mode of activity would promote the general anesthetic effects of etomidate. We recorded EEG activity and loss-of-righting reflex in transgenic mice expressing channel rhodopsin-2 on GABAergic neurons (ChR2-VGAT, n=8) and control, wild-type mice (C57BL/6J, n=8). On two consecutive days mice were randomly assigned to receive spindle-rhythm stimulation via an optical probe targeting the left reticular thalamic nucleus or no stimulation. After an initial 30-minute recording, mice were administered etomidate (12mg/kg, intraperitoneal) and recorded for 90 minutes with or without optical stimulation. Etomidate elicited an increase in 12-30Hz EEG power in wild-type and ChR2-VGAT mice for 20 minutes following administration (p<0.001). Optical spindle-rhythm stimulation prolonged the increase in 12-30Hz activity in ChR2-VGAT mice only (p=0.023). Spindle-rhythm stimulation also increased the incidence and duration of sleep spindle-like oscillations in ChR2-VGAT mice only (all p≤0.001). Despite the maintained anesthetic-like changes in EEG activity, optical spindle-rhythm stimulation was not associated with changes in the time to and duration of the loss-of-righting reflex, a behavioral endpoint of etomidate-induced general anesthesia in rodents.
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Naturalistic escape requires versatile context-specific flight with rapid evaluation of local geometry to identify and use efficient escape routes. It is unknown how spatial navigation and escape circuits are recruited to produce context-specific flight. Using mice, we show that activity in cholecystokinin-expressing hypothalamic dorsal premammillary nucleus (PMd-cck) cells is sufficient and necessary for context-specific escape that adapts to each environment’s layout. In contrast, numerous other nuclei implicated in flight only induced stereotyped panic-related escape. We reasoned the dorsal premammillary nucleus (PMd) can induce context-specific escape because it projects to escape and spatial navigation nuclei. Indeed, activity in PMd-cck projections to thalamic spatial navigation circuits is necessary for context-specific escape induced by moderate threats but not panic-related stereotyped escape caused by perceived asphyxiation. Conversely, the PMd projection to the escape-inducing dorsal periaqueductal gray projection is necessary for all tested escapes. Thus, PMd-cck cells control versatile flight, engaging spatial navigation and escape circuits.
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Background Hypersensitivity to general anaesthetics predicts adverse postoperative outcomes in patients. Hypoxia exerts extensive pathophysiological effects on the brain; however, whether hypoxia influences sevoflurane sensitivity and its underlying mechanisms remain poorly understood. Methods Mice were acclimated to hypoxia (oxygen 10% for 8 h day⁻¹) for 28 days and anaesthetised with sevoflurane; the effective concentrations for 50% of the animals (EC50) showing loss of righting reflex (LORR) and loss of tail-pinch withdrawal response (LTWR) were determined. Positron emission tomography–computed tomography, O-glycoproteomics, seahorse analysis, carbon-13 tracing, site-specific mutagenesis, and electrophysiological techniques were performed to explore the underlying mechanisms. Results Compared with the control group, the hypoxia-acclimated mice required higher concentrations of sevoflurane to present LORR and LTWR (EC50LORR: 1.61 [0.03]% vs 1.46 [0.04]%, P<0.01; EC50LTWR: 2.46 [0.14]% vs 2.22 [0.06]%, P<0.01). Hypoxia-induced reduction in sevoflurane sensitivity was correlated with elevation of protein O-linked N-acetylglucosamine (O-GlcNAc) modification in brain, especially in the thalamus, and could be abolished by 6-diazo-5-oxo-l-norleucine, a glutamine fructose-6-phosphate amidotransferase inhibitor, and mimicked by thiamet-G, a selective O-GlcNAcase inhibitor. Mechanistically, O-GlcNAcylation drives de novo synthesis of glutamine from glucose in astrocytes and promotes the glutamate–glutamine cycle, partially via glycolytic flux and activation of glutamine synthetase. Conclusions Intermittent hypoxia exposure decreased mouse sensitivity to sevoflurane anaesthesia through enhanced O-GlcNAc-dependent modulation of the glutamate–glutamine cycle in the brain.
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The preoptic area (POA) is necessary for sleep, but the fundamental POA circuits have remained elusive. Previous studies showed that galanin (GAL)- and GABA-producing neurons in the ventrolateral preoptic nucleus (VLPO) express cFos after periods of increased sleep and innervate key wake-promoting regions. Although lesions in this region can produce insomnia, high frequency photostimulation of the POAGAL neurons was shown to paradoxically cause waking, not sleep. Here we report that photostimulation of VLPOGAL neurons in mice promotes sleep with low frequency stimulation (1–4 Hz), but causes conduction block and waking at frequencies above 8 Hz. Further, optogenetic inhibition reduces sleep. Chemogenetic activation of VLPOGAL neurons confirms the increase in sleep, and also reduces body temperature. In addition, chemogenetic activation of VLPOGAL neurons induces short-latency sleep in an animal model of insomnia. Collectively, these findings establish a causal role of VLPOGAL neurons in both sleep induction and heat loss.
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Diurnal gene expression patterns underlie time of the day-specific functional specialization of tissues. However, available circadian gene expression atlases of a few organs are largely from nocturnal vertebrates. We report the diurnal transcriptome of 64 tissues, including 22 brain regions, sampled every 2 hours over 24 hours, from the primate Papio anubis (baboon). Genomic transcription was highly rhythmic with up to 81.7% of protein-coding genes showing daily rhythms in expression. In addition to tissue-specific gene expression, the rhythmic transcriptome imparts another layer of functional specialization. Most of ubiquitously expressed genes that participate in essential cellular functions exhibit rhythmic expression in a tissue-specific manner. The peak phases of rhythmic gene expression clustered around dawn and dusk with a “quiescent period” during early night. Our findings also unveil a different temporal organization of central and peripheral tissues between diurnal and nocturnal animals.
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The lateral habenula has been widely studied for its contribution in generating reward-related behaviors [1, 2]. We have found that this nucleus plays an unexpected role in the sedative actions of the general anesthetic propofol. The lateral habenula is a glutamatergic, excitatory hub that projects to multiple targets throughout the brain, including GABAergic and aminergic nuclei that control arousal [3-5]. When glutamate release from the lateral habenula in mice was genetically blocked, the ability of propofol to induce sedation was greatly diminished. In addition to this reduced sensitivity to propofol, blocking output from the lateral habenula caused natural non-rapid eye movement (NREM) sleep to become highly fragmented, especially during the rest ("lights on") period. This fragmentation was largely reversed by the dual orexinergic antagonist almorexant. We conclude that the glutamatergic output from the lateral habenula is permissive for the sedative actions of propofol and is also necessary for the consolidation of natural sleep.
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Mammalian sleep consists of distinct rapid eye movement (REM) and non-REM (NREM) states. The midbrain region ventrolateral periaqueductal gray (vlPAG) is known to be important for gating REM sleep, but the underlying neuronal mechanism is not well understood. Here, we show that activating vlPAG GABAergic neurons in mice suppresses the initiation and maintenance of REM sleep while consolidating NREM sleep, partly through their projection to the dorsolateral pons. Cell-type-specific recording and calcium imaging reveal that most vlPAG GABAergic neurons are strongly suppressed at REM sleep onset and activated at its termination. In addition to the rapid changes at brain state transitions, their activity decreases gradually between REM sleep and is reset by each REM episode in a duration-dependent manner, mirroring the accumulation and dissipation of REM sleep pressure. Thus, vlPAG GABAergic neurons powerfully gate REM sleep, and their firing rate modulation may contribute to the ultradian rhythm of REM/NREM alternation.
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Basic and clinical observations suggest that the caudal hypothalamus comprises a key node of the ascending arousal system, but the cell types underlying this are not fully understood. Here we report that glutamate-releasing neurons of the supramammillary region (SuMvglut2) produce sustained behavioral and EEG arousal when chemogenetically activated. This effect is nearly abolished following selective genetic disruption of glutamate release from SuMvglut2 neurons. Inhibition of SuMvglut2 neurons decreases and fragments wake, also suppressing theta and gamma frequency EEG activity. SuMvglut2 neurons include a subpopulation containing both glutamate and GABA (SuMvgat/vglut2) and another also expressing nitric oxide synthase (SuMNos1/Vglut2). Activation of SuMvgat/vglut2 neurons produces minimal wake and optogenetic stimulation of SuMvgat/vglut2 terminals elicits monosynaptic release of both glutamate and GABA onto dentate granule cells. Activation of SuMNos1/Vglut2 neurons potently drives wakefulness, whereas inhibition reduces REM sleep theta activity. These results identify SuMvglut2 neurons as a key node of the wake−sleep regulatory system.
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Sleep is an essential and phylogenetically conserved behavioral state, but it remains unclear to what extent genes identified in invertebrates also regulate vertebrate sleep. RFamide-related neuropeptides have been shown to promote invertebrate sleep, and here we report that the vertebrate hypothalamic RFamide neuropeptide VF (NPVF) regulates sleep in the zebrafish, a diurnal vertebrate. We found that NPVF signaling and npvf-expressing neurons are both necessary and sufficient to promote sleep, that mature peptides derived from the NPVF preproprotein promote sleep in a synergistic manner, and that stimulation of npvf-expressing neurons induces neuronal activity levels consistent with normal sleep. These results identify NPVF signaling and npvf-expressing neurons as a novel vertebrate sleep-promoting system and suggest that RFamide neuropeptides participate in an ancient and central aspect of sleep control.
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Activation of estrogen receptor beta (ERβ)-expressing neurons regulates the mammalian stress response via the hypothalamic-pituitary-adrenal (HPA) axis. These neurons densely populate the paraventricular nucleus of the hypothalamus (PVN). Recent research has revealed striking differences between rat and mouse PVN cytochemistry, but careful exploration of PVN ERβ neurons in mice has been hindered by a lack of specific ERβ antisera. Therefore, we used male and female transgenic mice expressing EGFP under the control of the mouse ERβ promoter (ERβ-EGFP) to examine the chemical architecture of PVN ERβ cells. Using immunohistochemistry, we found that 90% of ERβ-immunoreactivity (-ir) colocalized with EGFP. Cellular colocalization of EGFP with neuropeptides, transcription modulators, and neuronal tracers was examined throughout the PVN. ERβ-EGFP cells expressed oxytocin more abundantly in the rostral (71±3%) than caudal (33±8%) PVN. Arginine vasopressin colocalized with EGFP more often in females (18±3%) than males (4±1%). Moreover, estrogen receptor α-ir colocalized with ERβ-EGFP at low levels (15±3%). Using a corticotropin releasing hormone (CRH)-cre driver X tdTomato reporter mouse, we found a moderate colocalization with ERβ-ir (48±16%) in the middle PVN. Peripheral injection of fluorogold revealed that the rostral PVN ERβ-EGFP cells are neuroendocrine neurons whereas non-neuroendocrine (presumably pre-autonomic) ERβ-EGFP neurons predominated in the posterior PVN. These data demonstrate chemoarchitectural differences in ERβ neurons of the mouse PVN that are different from that previously described for the rat, thus, elucidating potential neuronal pathways involved in the regulation of the HPA axis in mice. This article is protected by copyright. All rights reserved.
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The lateral hypothalamic area (LHA) of the diencephalon is crucially involved in controlling instinctive behavior such as sleep–wake cycle and feeding behavior. LHA is a heterogeneous structure that contains spatially intermingled, genetically distinct cell populations. Among LHA neurons, orexin/hypocretin (OX) neuron is the key cell type that promotes waking, and specific loss of OX neurons results in narcolepsy. Melanin-concentrating hormone (MCH) containing neurons are known to be active during rapid eye movement (REM) sleep and stimulation of these neurons promotes REM sleep. Here we review the classical and more recent findings in this field and discuss the molecular and cellular network organization of LHA neurons that could ultimately regulate the switch between wakefulness and general states of sleep.
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Dopamine (DA) promotes wakefulness, and DA transporter inhibitors such as dextroamphetamine and methylphenidate are effective for increasing arousal and inducing reanimation, or active emergence from general anesthesia. DA neurons in the ventral tegmental area (VTA) are involved in reward processing, motivation, emotion, reinforcement, and cognition, but their role in regulating wakefulness is less clear. The current study was performed to test the hypothesis that selective optogenetic activation of VTA DA neurons is sufficient to induce arousal from an unconscious, anesthetized state. Floxed-inverse (FLEX)-Channelrhodopsin2 (ChR2) expression was targeted to VTA DA neurons in DA transporter (DAT)-cre mice (ChR2+ group; n = 6). Optical VTA stimulation in ChR2+ mice during continuous, steady-state general anesthesia (CSSGA) with isoflurane produced behavioral and EEG evidence of arousal and restored the righting reflex in 6/6 mice. Pretreatment with the D1 receptor antagonist SCH-23390 before optical VTA stimulation inhibited the arousal responses and restoration of righting in 6/6 ChR2+ mice. In control DAT-cre mice, the VTA was targeted with a viral vector lacking the ChR2 gene (ChR2- group; n = 5). VTA optical stimulation in ChR2- mice did not restore righting or produce EEG changes during isoflurane CSSGA in 5/5 mice. These results provide compelling evidence that selective stimulation of VTA DA neurons is sufficient to induce the transition from an anesthetized, unconscious state to an awake state, suggesting critical involvement in behavioral arousal.
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Dopaminergic ventral tegmental area (VTA) neurons are critically involved in a variety of behaviors that rely on heightened arousal, but whether they directly and causally control the generation and maintenance of wakefulness is unknown. We recorded calcium activity using fiber photometry in freely behaving mice and found arousal-state-dependent alterations in VTA dopaminergic neurons. We used chemogenetic and optogenetic manipulations together with polysomnographic recordings to demonstrate that VTA dopaminergic neurons are necessary for arousal and that their inhibition suppresses wakefulness, even in the face of ethologically relevant salient stimuli. Nevertheless, before inducing sleep, inhibition of VTA dopaminergic neurons promoted goal-directed and sleep-related nesting behavior. Optogenetic stimulation, in contrast, initiated and maintained wakefulness and suppressed sleep and sleep-related nesting behavior. We further found that different projections of VTA dopaminergic neurons differentially modulate arousal. Collectively, our findings uncover a fundamental role for VTA dopaminergic circuitry in the maintenance of the awake state and ethologically relevant sleep-related behaviors.
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There have been a number of advances in the search for the neural correlates of consciousness-the minimum neural mechanisms sufficient for any one specific conscious percept. In this Review, we describe recent findings showing that the anatomical neural correlates of consciousness are primarily localized to a posterior cortical hot zone that includes sensory areas, rather than to a fronto-parietal network involved in task monitoring and reporting. We also discuss some candidate neurophysiological markers of consciousness that have proved illusory, and measures of differentiation and integration of neural activity that offer more promising quantitative indices of consciousness.
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Optogenetic techniques are used widely to perturb and interrogate neural circuits in behaving animals, but illumination can have additional effects, such as the activation of endogenous opsins in the retina. We found that illumination, delivered deep into the brain via an optical fiber, evoked a behavioral artifact in mice performing a visually guided discrimination task. Compared with blue (473 nm) and yellow (589 nm) illumination, red (640 nm) illumination evoked a greater behavioral artifact and more activity in the retina, the latter measured with electrical recordings. In the mouse, the sensitivity of retinal opsins declines steeply with wavelength across the visible spectrum, but propagation of light through brain tissue increases with wavelength. Our results suggest that poor retinal sensitivity to red light was overcome by relatively robust propagation of red light through brain tissue and stronger illumination of the retina by red than by blue or yellow light. Light adaptation of the retina, via an external source of illumination, suppressed retinal activation and the behavioral artifact without otherwise impacting behavioral performance. In summary, long wavelength optogenetic stimuli are particularly prone to evoke behavioral artifacts via activation of retinal opsins in the mouse, but light adaptation of the retina can provide a simple and effective mitigation of the artifact.
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Histaminergic neurons in the tuberomammilary nucleus (TMN) of the hypothalamus form a widely projecting, wake-active network that sustains arousal. Yet most histaminergic neurons contain GABA. Selective siRNA knockdown of the vesicular GABA transporter (vgat, SLC32A1) in histaminergic neurons produced hyperactive mice with an exceptional amount of sustained wakefulness. Ablation of the vgat gene throughout the TMN further sharpened this phenotype. Optogenetic stimulation in the caudate-putamen and neocortex of "histaminergic" axonal projections from the TMN evoked tonic (extrasynaptic) GABAA receptor Cl(-) currents onto medium spiny neurons and pyramidal neurons. These currents were abolished following vgat gene removal from the TMN area. Thus wake-active histaminergic neurons generate a paracrine GABAergic signal that serves to provide a brake on overactivation from histamine, but could also increase the precision of neocortical processing. The long range of histamine-GABA axonal projections suggests that extrasynaptic inhibition will be coordinated over large neocortical and striatal areas. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
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Homeostasis is a biological principle for regulation of essential physiological parameters within a set range. Behavioural responses due to deviation from homeostasis are critical for survival, but motivational processes engaged by physiological need states are incompletely understood. We examined motivational characteristics of two separate neuron populations that regulate energy and fluid homeostasis by using cell-type-specific activity manipulations in mice. We found that starvation-sensitive AGRP neurons exhibit properties consistent with a negative-valence teaching signal. Mice avoided activation of AGRP neurons, indicating that AGRP neuron activity has negative valence. AGRP neuron inhibition conditioned preference for flavours and places. Correspondingly, deep-brain calcium imaging revealed that AGRP neuron activity rapidly reduced in response to food-related cues. Complementary experiments activating thirst-promoting neurons also conditioned avoidance. Therefore, these need-sensing neurons condition preference for environmental cues associated with nutrient or water ingestion, which is learned through reduction of negative-valence signals during restoration of homeostasis.
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Do sedatives engage natural sleep pathways? It is usually assumed that anesthetic-induced sedation and loss of righting reflex (LORR) arise by influencing the same circuitry to lesser or greater extents. For the α2 adrenergic receptor agonist dexmedetomidine, we found that sedation and LORR were in fact distinct states, requiring different brain areas: the preoptic hypothalamic area and locus coeruleus (LC), respectively. Selective knockdown of α2A adrenergic receptors from the LC abolished dexmedetomidine-induced LORR, but not sedation. Instead, we found that dexmedetomidine-induced sedation resembled the deep recovery sleep that follows sleep deprivation. We used TetTag pharmacogenetics in mice to functionally mark neurons activated in the preoptic hypothalamus during dexmedetomidine-induced sedation or recovery sleep. The neuronal ensembles could then be selectively reactivated. In both cases, non-rapid eye movement sleep, with the accompanying drop in body temperature, was recapitulated. Thus, α2 adrenergic receptor-induced sedation and recovery sleep share hypothalamic circuitry sufficient for producing these behavioral states.
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Rapid eye movement (REM) sleep is an important component of the natural sleep/wake cycle, yet the mechanisms that regulate REM sleep remain incompletely understood. Cholinergic neurons in the mesopontine tegmentum have been implicated in REM sleep regulation, but lesions of this area have had varying effects on REM sleep. Therefore, this study aimed to clarify the role of cholinergic neurons in the pedunculopontine tegmentum (PPT) and laterodorsal tegmentum (LDT) in REM sleep generation. Selective optogenetic activation of cholinergic neurons in the PPT or LDT during non-REM (NREM) sleep increased the number of REM sleep episodes and did not change REM sleep episode duration. Activation of cholinergic neurons in the PPT or LDT during NREM sleep was sufficient to induce REM sleep.
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