Diazepam-induced changes in sleep: role of the alpha 1 GABA(A) receptor subtype

Targeting Sleep Physiology to Modulate Glymphatic Brain Clearance

Sleep has been postulated to play an important role in the removal of potentially neurotoxic molecules, such as amyloid-β, from the brain via the glymphatic system. Disturbed sleep, on the other hand, may contribute to the accumulation of neurotoxins in brain tissue, eventually leading to neuronal death. A bidirectional relationship has been proposed between impaired sleep and neurodegenerative processes, which start years before the onset of clinical symptoms associated with conditions like Alzheimer's and Parkinson's diseases. Given the heavy burden these conditions place on society, it is imperative to develop interventions that promote efficient brain clearance, thereby potentially aiding in the prevention or slowing of neurodegeneration. In this review, we explore whether the metabolic clearance function of sleep can be enhanced through sensory (e.g., auditory, vestibular) or transcranial (e.g., magnetic, ultrasound, infrared light) stimulation, as well as pharmacological (e.g., antiepileptics) and behavioral (e.g., sleeping position, physical exercise, cognitive intervention) modulation of sleep physiology. A particular focus is placed on strategies to enhance slow-wave activity during nonrapid eye movement sleep as a driver of glymphatic brain clearance. Overall, this review provides a comprehensive overview on the potential preventative and therapeutic applications of sleep interventions in combating neurodegeneration, cognitive decline, and dementia.

The effects of diazepam on sleep depend on the photoperiod

Daylength (i.e., photoperiod) provides essential information for seasonal adaptations of organisms. Earlier studies have demonstrated that photoperiod influences sleep in several species. Notably, photoperiod can change the excitatory/inhibitory balance in the brain, with long photoperiod exhibiting increased γ-aminobutyric-acid (GABA)-mediated excitation. In this study, we first investigated whether different photoperiods influence sleep and the sleep electroencephalogram (EEG) in mice, and, subsequently, whether these photoperiods alter GABAergic functioning by treating mice with diazepam (3 mg/kg, i.p.). EEG and electromyogram (EMG) recordings were conducted in mice well-adapted to long or short photoperiod (16:8 vs. 8:16 light-dark cycle) in baseline conditions, after 4-h sleep deprivation, and following diazepam administration. Different photoperiods led to a redistribution of sleep and wakefulness in 24-h albeit without altering the overall amount of vigilance states; during darkness, mice exposed to the long photoperiod were more awake and showed very little rapid-eye-movement (REM) sleep compared to the short photoperiod. Furthermore, an overall lower EEG power density, across all vigilance states, was found in the long compared to short photoperiod. After diazepam treatment, slow-wave-activity (SWA) in NREM sleep was suppressed independent of the photoperiod. However, following diazepam administration, mice showed more REM sleep in the short photoperiod, and increased EEG power density in the slower frequencies (2.5-7 Hz), during wakefulness in the long photoperiod. These results demonstrate that photoperiod can affect the diazepam-induced changes on sleep architecture and EEG, suggesting that treatments with GABAA agonists exert dissimilar effects depending on the photoperiod. Future studies are warranted to explore potential photoperiod effects in humans which could have consequences for the treatment of anxiety and sleep disturbances.

Modulation of sleep/wake patterns by gephyrin phosphorylation status

Sleep/wake cycles intricately shape physiological activities including cognitive brain functions, yet the precise molecular orchestrators of sleep remain elusive. Notably, the clinical impact of benzodiazepine drugs underscores the pivotal role of GABAergic neurotransmission in sleep regulation. However, the specific contributions of distinct GABAA receptor subtypes and their principal scaffolding protein, gephyrin, in sleep dynamics remain unclear. The evolving role of synaptic phospho-proteome alterations at excitatory and inhibitory synapses suggests a potential avenue for modulating gephyrin and, consequently, GABAARs for sleep through on-demand kinase recruitment. Our study unveils the distinctive roles of two prevalent GABAA receptor subtypes, α1- and α2-GABAARs, in influencing sleep duration and electrical sleep activity. Notably, the absence of α1-GABAARs emerges as central in sleep regulation, manifesting significant alterations in both non-rapid eye movement (NREM) and rapid eye movement (REM) sleep during dark or active phases, accompanied by altered electroencephalogram (EEG) patterns across various frequencies. Gephyrin proteomics analysis reveals sleep/wake-dependent interactions with a repertoire of known and novel kinases. Crucially, we identify the regulation of gephyrin interaction with ERK1/2, and phosphorylations at serines 268 and 270 are dictated by sleep/wake cycles. Employing AAV-eGFP-gephyrin or its phospho-null variant (S268A/S270A), we disrupt sleep either globally or locally to demonstrate gephyrin phosphorylation as a sleep regulator. In summary, our findings support the local cortical sleep hypothesis and we unveil a molecular mechanism operating at GABAergic synapses, providing critical insights into the intricate regulation of sleep.

Sedative Effects of Daidzin, Possibly Through the GABAA Receptor Interaction Pathway: In Vivo Approach with Molecular Dynamic Simulations

The soy isoflavone daidzin (DZN) has been considered a hopeful bioactive compound having diverse biological activities, including anxiolytic, memory-enhancing, and antiepileptic effects, in experimental animals. However, its sedative and hypnotic effects are yet to be discovered. This study aimed to evaluate its sedative/hypnotic effect on Swiss mice. Additionally, in silico studies were also performed to see the possible molecular mechanisms behind the tested neurological effect. For this, male Swiss albino mice were treated with DZN (5, 10, or 20 mg/kg) intraperitoneally (i.p.) with or without the standard GABAergic medication diazepam (DZP) and/or flumazenil (FLU) and checked for the onset and duration of sleeping time using thiopental sodium-induced as well as DZP-induced sleeping tests. A molecular docking study was also performed to check its interaction capacity with the α1 and β2 subunits of the GABAA receptor. Findings suggest that DZN dose-dependently and significantly reduced the latency while increasing the duration of sleep in animals. In combination therapy, DZN shows synergistic effects with the DZP-2 and DZP-2 + FLU-0.01 groups, resulting in significantly (p < 0.05) reduced latency and increased sleep duration. Further, molecular docking studies demonstrate that DZN has a strong binding affinity of - 7.2 kcal/mol, which is closer to the standard ligand DZP (- 8.3 kcal/mol) against the GABAA (6X3X) receptor. Molecular dynamic simulations indicated stability and similar binding locations for DZP and DZN with 6X3X. In conclusion, DZN shows sedative effects on Swiss mice, possibly through the GABAA receptor interaction pathway.

Assessment of sedative activity of fraxin: In vivo approach along with receptor binding affinity and molecular interaction with GABAergic system

Insomnia is a sleep disorder in which you have trouble falling and/or staying asleep. This research aims to evaluate the sedative effects of fraxin (FX) on sleeping mice induced by thiopental sodium (TS). In addition, a molecular docking study was conducted to investigate the molecular processes underlying these effects. The study used adult male Swiss albino mice and administered FX (10 and 20 mg/kg, i.p.) and diazepam (DZP) (2 mg/kg) either separately or in combination within the different groups to examine their modulatory effects. After a period of 30 min, the mice that had been treated were administered (TS: 20 mg/kg, i.p.) to induce sleep. The onset of sleep for the mice and the length of their sleep were manually recorded. Additionally, a computational analysis was conducted to predict the role of gamma-aminobutyric acid (GABA) receptors in the sleep process and evaluate their pharmacokinetics and toxicity. The outcomes indicated that FX extended the length of sleep and reduced the time it took to fall asleep. When the combined treatment of FX and DZP showed synergistic sedative action. Also, FX had a binding affinity of -7.2 kcal/mol, while DZP showed -8.4 kcal/mol. The pharmacokinetic investigation of FX demonstrated favorable drug-likeness and strong pharmacokinetic characteristics. Ultimately, FX demonstrated a strong sedative impact in the mouse model, likely via interacting with the GABAA receptor pathways.

Sleep alterations as a function of 88 health indicators

BACKGROUND

Alterations in sleep have been described in multiple health conditions and as a function of several medication effects. However, evidence generally stems from small univariate studies. Here, we apply a large-sample, data-driven approach to investigate patterns between in sleep macrostructure, quantitative sleep EEG, and health.

METHODS

We use data from the MrOS Sleep Study, containing polysomnography and health data from a large sample (N = 3086) of elderly American men to establish associations between sleep macrostructure, the spectral composition of the electroencephalogram, 38 medical disorders, 2 health behaviors, and the use of 48 medications.

RESULTS

Of sleep macrostructure variables, increased REM latency and reduced REM duration were the most common findings across health indicators, along with increased sleep latency and reduced sleep efficiency. We found that the majority of health indicators were not associated with objective EEG power spectral density (PSD) alterations. Associations with the rest were highly stereotypical, with two principal components accounting for 85-95% of the PSD-health association. PC1 consists of a decrease of slow and an increase of fast PSD components, mainly in NREM. This pattern was most strongly associated with depression/SSRI medication use and age-related disorders. PC2 consists of changes in mid-frequency activity. Increased mid-frequency activity was associated with benzodiazepine use, while decreases were associated with cardiovascular problems and associated medications, in line with a recently proposed hypothesis of immune-mediated circadian demodulation in these disorders. Specific increases in sleep spindle frequency activity were associated with taking benzodiazepines and zolpidem. Sensitivity analyses supported the presence of both disorder and medication effects.

CONCLUSIONS

Sleep alterations are present in various health conditions.

Aralia continentalis Root Enhances Non-Rapid Eye Movement Sleep by Activating GABAA Receptors

Aralia continentalis exhibits various biological activities; however, their sleep-promoting effects have not been previously reported. In this study, we evaluated the hypnotic effects and sleep-wake profiles of A. continentalis root (KS-126) using a pentobarbital-induced sleep-acceleration test and polysomnographic recordings. Additionally, we investigated the molecular mechanism of KS-126 through patch-clamp electrophysiology. Our polysomnographic recordings revealed that KS-126 not only accelerated the onset of non-rapid eye movement sleep (NREMS) but also extends its duration. Considering the temporal dynamics of the sleep-wake stages, during the initial and subsequent periods KS-126 extended NREMS duration and decreased wakefulness, thereby enhancing sleep-promoting effects. Furthermore, the assessment of sleep quality via analysis of electroencephalogram power density indicated that KS-126 did not significantly alter sleep intensity. Finally, we found that KS-126 enhanced GABAA receptor-mediated synaptic responses in primary hippocampal neurons, leading to an increase in the percentage of the GABA current. This effect was not affected by the selective benzodiazepine receptor antagonist flumazenil, but was entirely inhibited by the GABAA receptor antagonist bicuculline. In conclusion, KS-126 extends the duration of NREMS without altering its intensity by prolonging GABAergic synaptic transmission, which modulates GABAA receptor function.

Pharmaco-EEG analysis of ligands varying in selectivity for α1 subunit-containing GABAA receptors during the active phase in rats

RATIONALE

Benzodiazepines are known to evoke changes in cortical electrophysiological activity that can be correlated with action at distinct γ-aminobutyric acid type A (GABAA) receptor subtypes.

OBJECTIVES

We used electroencephalography (EEG) paired with electromyography (EMG) to evaluate the role of α1 subunit-containing GABAA receptors (α1GABAARs) in benzodiazepine-induced sedation and changes in EEG band frequencies during the active phase of the light/dark cycle.

METHODS

Male Sprague-Dawley rats (N = 4/drug) were surgically instrumented with EEG/EMG electrodes. The rats were injected i.p. with zolpidem, an α1GABAAR-preferring compound, or L-838,417, which has selective efficacy for α2/3/5 subunit-containing GABAARs (i.e., α1GABAAR-sparing compound), in comparison with the non-selective benzodiazepine, triazolam.

RESULTS

All ligands evaluated induced changes in sleep-wake states during the active phase consistent with an increase in slow-wave sleep (SWS). The degree of SWS increase appeared to be related to the magnitude of delta power band changes induced by the ligands, with the strongest effects engendered by the α1GABAAR-preferring drug zolpidem and the weakest effects by the α1GABAAR-sparing compound, L-838,417. Consistent with other research, a selective increase in beta band power was observed with L-838,417, which may be associated with α2GABAAR-mediated anxiolysis.

CONCLUSIONS

Overall, these findings support the establishment of pharmaco-EEG "signatures" for identifying subtype-selective GABAA modulators in vivo.

Quercetin Antagonizes the Sedative Effects of Linalool, Possibly through the GABAergic Interaction Pathway

Sedatives promote calmness or sleepiness during surgery or severely stressful events. In addition, depression is a mental health issue that negatively affects emotional well-being. A group of drugs called anti-depressants is used to treat major depressive illnesses. The aim of the present work was to evaluate the effects of quercetin (QUR) and linalool (LIN) on thiopental sodium (TS)-induced sleeping mice and to investigate the combined effects of these compounds using a conventional co-treatment strategy and in silico studies. For this, the TS-induced sleeping mice were monitored to compare the occurrence, latency, and duration of the sleep-in response to QUR (10, 25, 50 mg/kg), LIN (10, 25, 50 mg/kg), and diazepam (DZP, 3 mg/kg, i.p.). Moreover, an in silico investigation was undertaken to assess this study's putative modulatory sedation mechanism. For this, we observed the ability of test and standard medications to interact with various gamma-aminobutyric acid A receptor (GABA_A) subunits. Results revealed that QUR and LIN cause dose-dependent antidepressant-like and sedative-like effects in animals, respectively. In addition, QUR-50 mg/kg and LIN-50 mg/kg and/or DZP-3 mg/kg combined were associated with an increased latency period and reduced sleeping times in animals. Results of the in silico studies demonstrated that QUR has better binding interaction with GABA_A α3, β1, and γ2 subunits when compared with DZP, whereas LIN showed moderate affinity with the GABA_A receptor. Taken together, the sleep duration of LIN and DZP is opposed by QUR in TS-induced sleeping mice, suggesting that QUR may be responsible for providing sedation-antagonizing effects through the GABAergic interaction pathway.

Pharmacological Analysis of GABAA Receptor and Sigma1R Chaperone Interaction: Research Report I-Investigation of the Anxiolytic, Anticonvulsant and Hypnotic Effects of Allosteric GABAA Receptors' Ligands

Two groups of facts have been established in previous drug development studies of the non-benzodiazepine anxiolytic fabomotizole. First, fabomotizole prevents stress-induced decrease in binding ability of the GABAA receptor's benzodiazepine site. Second, fabomotizole is a Sigma1R chaperone agonist, and exposure to Sigma1R antagonists blocks its anxiolytic effect. To prove our main hypothesis of Sigma1R involvement in GABAA receptor-dependent pharmacological effects, we performed a series of experiments on BALB/c and ICR mice using Sigma1R ligands to study anxiolytic effects of benzodiazepine tranquilizers diazepam (1 mg/kg i.p.) and phenazepam (0.1 mg/kg i.p.) in the elevated plus maze test, the anticonvulsant effects of diazepam (1 mg/kg i.p.) in the pentylenetetrazole-induced seizure model, and the hypnotic effects of pentobarbital (50 mg/kg i.p.). Sigma1R antagonists BD-1047 (1, 10, and 20 mg/kg i.p.), NE-100 (1 and 3 mg/kg i.p.), and Sigma1R agonist PRE-084 (1, 5, and 20 mg/kg i.p.) were used in the experiments. Sigma1R antagonists have been found to attenuate while Sigma1R agonists can enhance GABAARs-dependent pharmacological effects.

The importance of ligand gated ion channels in sleep and sleep disorders

On average, humans spend about 26 years of their life sleeping. Increased sleep duration and quality has been linked to reduced disease risk; however, the cellular and molecular underpinnings of sleep remain open questions. It has been known for some time that pharmacological modulation of neurotransmission in the brain can promote either sleep or wakefulness thereby providing some clues about the molecular mechanisms at play. However, the field of sleep research has developed an increasingly detailed understanding of the requisite neuronal circuitry and key neurotransmitter receptor subtypes, suggesting that it may be possible to identify next generation pharmacological interventions to treat sleep disorders within this same space. The aim of this work is to examine the latest physiological and pharmacological findings highlighting the contribution of ligand gated ion channels including the inhibitory GABA_A and glycine receptors and excitatory nicotinic acetylcholine receptors and glutamate receptors in the sleep-wake cycle regulation. Overall, a better understanding of ligand gated ion channels in sleep will help determine if these highly druggable targets could facilitate a better night's sleep.

The GABAA receptor modulator zolpidem augments hippocampal-prefrontal coupling during non-REM sleep

Benzodiazepines and 'Z-drugs' (including zolpidem and zopiclone) are GABAA receptor (GABAAR) positive modulators commonly prescribed as hypnotics to treat insomnia and/or anxiety. However, alongside sedation, augmenting GABAAR function may also alter coordinated neuronal activity during sleep, thereby influencing sleep-dependent processes including memory consolidation. We used simultaneous recordings of neural population activity from the medial prelimbic cortex (PrL) and CA1 of the dorsal hippocampus (dCA1) of naturally sleeping rats to detail the effects of zolpidem on network activity during the cardinal oscillations of non-REM sleep. For comparison, we also characterized the effects of diazepam and 4,5,6,7-tetrahydroisoxazolo(5,4-c)pyridin-3-ol (THIP/gaboxadol), which acts predominantly at extra-synaptic GABAARs. Zolpidem and THIP significantly increased the amplitudes of slow-waves, which were attenuated by diazepam. Zolpidem increased hippocampal ripple density whereas diazepam decreased both ripple density and intrinsic frequency. While none of the drugs affected thalamocortical spindles in isolation, zolpidem augmented the temporal coordination between slow-waves and spindles. At the cellular level, analyses of spiking activity from 523 PrL and 579 dCA1 neurons revealed that zolpidem significantly enhanced synchronized pauses in cortical firing during slow-wave down states, while increasing correlated activity within and between dCA1 and PrL populations. Of the drugs compared here, zolpidem was unique in augmenting coordinated activity within and between hippocampus and neocortex during non-REM sleep. Zolpidem's enhancement of hippocampal-prefrontal coupling may reflect the cellular basis of its potential to modulate offline memory processing.

Application of gabapentinoids and novel compounds for the treatment of benzodiazepine dependence: the glutamatergic model

BACKGROUND

Current approaches for managing benzodiazepine (BZD) withdrawal symptoms are daunting for clinicians and patients, warranting novel treatment and management strategies. This review discusses the pharmacodynamic properties of BZDs, gabapentinoids (GBPs), endozepines, and novel GABAergic compounds associated with potential clinical benefits for BZD-dependent patients. The objective of this study was to review the complex neuromolecular changes occurring within the GABAergic and glutamatergic systems during the BZD tolerance and withdrawal periods while also examining the mechanism by which GBPs and alternative pharmacological therapies may attenuate withdrawal symptoms.

METHODS AND RESULTS

An elaborative literature review was conducted using multiple platforms, including the National Center for Biotechnology (NCBI), AccessMedicine, ScienceDirect, pharmacology textbooks, clinical trial data, case reports, and PubChem. Our literature analysis revealed that many distinctive neuroadaptive mechanisms are involved in the GABAergic and glutamatergic systems during BZD tolerance and withdrawal. Based on this data, we hypothesize that GBPs may attenuate the overactive glutamatergic system during the withdrawal phase by an indirect presynaptic glutamatergic mechanism dependent on the α₂δ₁ subunit expression.

CONCLUSIONS

GBPs may benefit individuals undergoing BZD withdrawal, given that the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor current significantly increases during abrupt BZD withdrawal in animal studies. This may be a conceivable explanation for the effectiveness of GBPs in treating both alcohol withdrawal symptoms and BZD withdrawal symptoms in some recent studies. Finally, natural and synthetic GABAergic compounds with unique pharmacodynamic properties were found to exert potential clinical benefits as BZD substitutes in animal studies, though human studies are lacking.

Curcuminoids, a major turmeric component, have a sleep-enhancing effect by targeting the histamine H1 receptor

Turmeric (Curcuma longa) had been considered as a universal panacea in functional foods and traditional medicines. In recent, the sedative-hypnotic effect of turmeric extract (TE) was reported. However, sleep-promoting compounds in TE have been not yet demonstrated. Curcuminoids (curcumin, demethoxycurcumin, and bisdemethoxycurcumin) are the major constituents of turmeric being responsible for its various biological activities. Therefore, they can be first assumed to be sedative-hypnotic compounds of TE. In the present study, we aimed to investigate the effects and underlying mechanisms of curcuminoids and each constituent on the sleep-wake cycle of mice. Molecular docking studies, histamine H1 receptor (H1R) binding assays, and H1R knockout animal studies were used to investigate the molecular mechanisms underlying the sleep-promoting effects. Curcuminoids and their constituents reduced sleep latency and increased sleep duration in the pentobarbital-induced sleep test in mice. In addition, curcuminoids significantly increased the duration of NREMS and reduced sleep latency without altering the REMS and delta activity. Curcumin, demethoxycurcumin, and bisdemethoxycurcumin were predicted to interact with H1R in the molecular model. In the binding affinity assay, we found that curcuminoids, as well as their constituents, significantly bind to H1R with the K_i value of 1.49 μg mL^-1. Furthermore, sleep latency was reduced and NREMS frequency was increased following curcuminoid administration in wild-type mice but not in H1R knockout mice. Therefore, we conclude that curcuminoids reduce sleep latency and enhance the quantity of NREMS by acting as modulators of H1R, indicating their usefulness in treating insomnia.

Effects of Green Kiwifruit Peel Extract on Sleep-Wake Profiles in Mice: A Polysomnographic Study Based on Electroencephalogram and Electromyogram Recordings

In the previous study, it was reported that green kiwifruit peel ethanol extract (GKPEE) increases sleep duration and decreases sleep latency in pentobarbital-treated mice. The pentobarbital-induced sleep test can be used to verify sleep quantity, which includes factors such as sleep duration and latency, but not sleep quality. In the present study, the sleep-promoting effects of GKPEE were investigated by the analysis of electroencephalogram (EEG) and electromyogram in mice and were compared with the results of diazepam (DZP), a representative sedative-hypnotic agent. The acute administration of GKPEE (250, 500 and 1000 mg/kg) increased the amount of non-rapid eye movement sleep (NREMS) and decreased sleep latency in a dose-dependent manner. The effect of GKPEE at 1000 mg/kg produced persistently significantly different results until the second hour of time-course changes. In particular, GKPEE did not produce any change in delta activity compared to DZP. Furthermore, sub-chronic administration (15 days) of GKPEE (500 mg/kg) continued sleep-promoting effects, whilst the EEG power density of NREMS did not show significant differences, indicating that there were no tolerance phenomena. Our findings suggest that GKPEE may be a promising natural sleep aid for treating sleep disorders. In addition, considering the number of by-products discarded each year by the food industry, the application of GKPEE here contributes to the utilization of processed kiwifruit by-products and can help to solve environmental problems.

Trihexyphenidyl increases delta activity in non-rapid eye movement sleep without impairing cognitive function in rodent models

Both human and rodent studies suggest the link between non-rapid eye movement (NREM) sleep and cognition. Recent study indicated that selective activation of cholinergic neurons in basal forebrain inhibits electroencephalogram (EEG) delta power and shortens NREM sleep. In the current study, we aimed to test the pharmacological effect of trihexyphenidyl (THP), a selective muscarinic M1 receptor antagonist, on EEG power spectra and sleep with or without the selective activation of basal forebrain cholinergic neurons. THP (1, 2, and 3 mg/kg) was administrated intraperitoneally in natural sleep phase. Basal forebrain cholinergic neurons expressing modified G protein-coupled muscarinic receptors (hM3Dq) were activated by intraperitoneal injection of clozapine-N-oxide in ChAT-IRES-Cre mice. EEG and electromyogram (EMG) signals were recorded in freely moving mice to analyze EEG power spectrum and sleep hypnogram. Y-maze and novel object recognition tests were used for testing cognition. THP 1 mg/kg significantly increased EEG delta power and facilitated NREM sleep in wildtype mice, while THP 3 mg/kg was required in ChAT-IRES-Cre mice treated with clozapine-N-oxide. THP with dosage up to 8 mg/kg did not induce cognitive impairments in wildtype mice. EEG delta power of NREM sleep is often used as an indicator of sleep depth or sleep quality, which tightly link with sleep-dependent cognition. Taken together, the data collected from rodents hinted that, THP could possibly be used as the NREM sleep facilitator in humans.

Association between abnormal brain oscillations and cognitive performance in patients with bipolar disorder; Molecular mechanisms and clinical evidence

Brain oscillations have gained great attention in neuroscience during recent decades as functional building blocks of cognitive-sensory processes. Research has shown that oscillations in "alpha," "beta," "gamma," "delta," and "theta" frequency windows are highly modified in brain pathology, including in patients with cognitive impairment like bipolar disorder (BD). The study of changes in brain oscillations can provide fundamental knowledge for exploring neurophysiological biomarkers in cognitive impairment. The present article reviews findings from the role and molecular basis of abnormal neural oscillation and synchronization in the symptoms of patients with BD. An overview of the results clearly demonstrates that, in cognitive-sensory processes, resting and evoked/event-related electroencephalogram (EEG) spectra in the delta, theta, alpha, beta, and gamma bands are abnormally changed in patients with BD showing psychotic features. Abnormal oscillations have been found to be associated with several neural dysfunctions and abnormalities contributing to BD, including abnormal GABAergic neurotransmission signaling, hippocampal cell discharge, abnormal hippocampal neurogenesis, impaired cadherin and synaptic contact-based cell adhesion processes, extended lateral ventricles, decreased prefrontal cortical gray matter, and decreased hippocampal volume. Mechanistically, impairment in calcium voltage-gated channel subunit alpha1 I, neurotrophic tyrosine receptor kinase proteins, genes involved in brain neurogenesis and synaptogenesis like WNT3 and ACTG2, genes involved in the cell adhesion process like CDH12 and DISC1, and gamma-aminobutyric acid (GABA) signaling have been reported as the main molecular contributors to the abnormalities in resting-state low-frequency oscillations in BD patients. Findings also showed the association of impaired synaptic connections and disrupted membrane potential with abnormal beta/gamma oscillatory activity in patients with BD. Of note, the synaptic GABA neurotransmitter has been found to be a fundamental requirement for the occurrence of long-distance synchronous gamma oscillations necessary for coordinating the activity of neural networks between various brain regions. This article is protected by copyright. All rights reserved.

Sleep disturbances are associated with cortical and subcortical atrophy in alcohol use disorder

Sleep disturbances are prominent in patients with alcohol use disorder (AUD) and predict relapse. So far, the mechanisms underlying sleep disruptions in AUD are poorly understood. Because sleep-related regions vastly overlap with regions, where patients with AUD showed pronounced grey matter (GM) reduction; we hypothesized that GM structure could contribute to sleep disturbances associated with chronic alcohol use. We combined sleep EEG recording and high-resolution structural brain imaging to examine the GM-sleep associations in 36 AUD vs. 26 healthy controls (HC). The patterns of GM-sleep associations differed for N3 vs. REM sleep and for AUD vs. HC. For cortical thickness (CT), CT-sleep associations were significant in AUD but not in HC and were lateralized such that lower CT in right hemisphere was associated with shorter N3, whereas in left hemisphere was associated with shorter REM sleep. For the GM density (GMD), we observed a more extensive positive GMD-N3 association in AUD (right orbitofrontal cortex, cerebellum, dorsal cingulate and occipital cortex) than in HC (right orbitofrontal cortex), and the GMD-REM association was positive in AUD (midline, motor and paralimbic regions) whereas negative in HC (the left supramarginal gyrus). GM structure mediated the effect of chronic alcohol use on the duration of N3 and the age by alcohol effect on REM sleep. Our findings provide evidence that sleep disturbances in AUD were associated with GM reductions. Targeting sleep-related regions might improve sleep in AUD and enhance sleep-induced benefits in cognition and emotional regulation for recovery.

Kv3.1 channels regulate the rate of critical period plasticity

Experience-dependent plasticity within visual cortex is controlled by postnatal maturation of inhibitory circuits, which are both morphologically diverse and precisely connected. Gene-targeted disruption of the voltage-dependent potassium channel K_v3.1 broadens action potentials and reduces net inhibitory function of parvalbumin (PV)-positive GABA subtypes within the neocortex. In mice lacking K_v3.1, the rate of input loss from an eye deprived of vision was slowed two-fold, despite otherwise normal critical period timecourse and receptive field properties. Rapid ocular dominance plasticity was restored by local or systemic enhancement of GABAergic transmission with acute benzodiazepine infusion. Diazepam instead exacerbated a global suppression of slow-wave oscillations during sleep described previously in these mutant mice, which therefore did not account for the rescued plasticity. Rapid ocular dominance shifts closely reflected K_v3.1 gene dosage that prevented prolonged spike discharge of their target pyramidal cells in vivo or the spike amplitude decrement of fast-spiking cells during bouts of high-frequency firing in vitro. Late postnatal expression of this unique channel in fast-spiking interneurons thus subtly regulates the speed of critical period plasticity with implications for mental illnesses.

Diazepam effects on local cortical neural activity during sleep in mice

GABA-ergic neurotransmission plays a key role in sleep regulatory mechanisms and in brain oscillations during sleep. Benzodiazepines such as diazepam are known to induce sedation and promote sleep, however, EEG spectral power in slow frequencies is typically reduced after the administration of benzodiazepines or similar compounds. EEG slow waves arise from a synchronous alternation between periods of cortical network activity (ON) and silence (OFF), and represent a sensitive marker of preceding sleep-wake history. Yet it remains unclear how benzodiazepines act on cortical neural activity during sleep. To address this, we obtained chronic recordings of local field potentials and multiunit activity (MUA) from deep cortical layers of the primary motor cortex in freely behaving mice after diazepam injection. We found that the amplitude of individual LFP slow waves was significantly reduced after diazepam injection and was accompanied by a lower incidence and duration of the corresponding neuronal OFF periods. Further investigation suggested that this is due to a disruption in the synchronisation of cortical neurons. Our data suggest that the state of global sleep and local cortical synchrony can be dissociated, and that the brain state induced by benzodiazepines is qualitatively different from spontaneous physiological sleep.

Region-specific and dose-specific effects of chronic haloperidol exposure on [3H]-flumazenil and [3H]-Ro15-4513 GABAA receptor binding sites in the rat brain

Postmortem studies suggest that schizophrenia is associated with abnormal expression of specific GABAA receptor (GABAAR) α subunits, including α5GABAAR. Positron emission tomography (PET) measures of GABAAR availability in schizophrenia, however, have not revealed consistent alterations in vivo. Animal studies using the GABAAR agonist [3H]-muscimol provide evidence that antipsychotic drugs influence GABAAR availability, in a region-specific manner, suggesting a potential confounding effect of these drugs. No such data, however, are available for more recently developed subunit-selective GABAAR radioligands. To address this, we combined a rat model of clinically relevant antipsychotic drug exposure with quantitative receptor autoradiography. Haloperidol (0.5 and 2 mg/kg/day) or drug vehicle were administered continuously to adult male Sprague-Dawley rats via osmotic mini-pumps for 28 days. Quantitative receptor autoradiography was then performed postmortem using the GABAAR subunit-selective radioligand [3H]-Ro15-4513 and the non-subunit selective radioligand [3H]-flumazenil. Chronic haloperidol exposure increased [3H]-Ro15-4513 binding in the CA1 sub-field of the rat dorsal hippocampus (p<0.01; q<0.01; d=+1.3), which was not dose-dependent. [3H]-flumazenil binding also increased in most rat brain regions (p<0.05; main effect of treatment), irrespective of the haloperidol dose. These data confirm previous findings that chronic haloperidol exposure influences the specific binding of non-subtype selective GABAAR radioligands and is the first to demonstrate a potential effect of haloperidol on the binding of a α1/5GABAAR-selective radioligand. Although caution should be exerted when extrapolating results from animals to patients, our data support a view that exposure to antipsychotics may be a confounding factor in PET studies of GABAAR in the context of schizophrenia.

Sleep-enhancing Effects of Phytoncide Via Behavioral, Electrophysiological, and Molecular Modeling Approaches

Sleep is indispensable for living animals to live and maintain a normal life. Due to the growing number of people suffering from sleep disorders such as insomnia, there have been increasing interests in environmentally friendly therapeutic approaches for sleep disorders to avoid any side effects of pharmacological treatment using synthetic hypnotics. It has been widely accepted that the various beneficial effects of forest, such as relieving stress and anxiety and enhancing immune system function, are caused by plant-derived products, also known as phytoncide. Recently, it has been reported that the sleep-enhancing effects of phytoncide are derived from pine trees such as (-)-α-pinene and 3-carene. These are the major constituents of pine tree that potentiate the inhibitory synaptic responses by acting as a positive modulator for GABA_A-BZD receptor. In this review, we discuss the effects of phytoncide on sleep and review the latest approaches of sleep-related behavioral assay, electrophysiological recording, and molecular modeling technique.

Dieckol, a Major Marine Polyphenol, Enhances Non-Rapid Eye Movement Sleep in Mice via the GABAA-Benzodiazepine Receptor

We had previously demonstrated that phlorotannins, which are marine polyphenols, enhance sleep in mice via the GABA_A-benzodiazepine (BZD) receptor. Among the constituents of phlorotannin, dieckol is a major marine polyphenol from the brown alga Ecklonia cava. Although phlorotannins are known to exert hypnotic effects, the sleep-enhancing effect of dieckol has not yet been determined. We evaluated the effect of dieckol on sleep-wake state of mice by analyzing electroencephalograms (EEGs) and electromyograms. Flumazenil, a GABA_A-BZD antagonist, was used to investigate the molecular mechanism underlying the effects of dieckol on sleep. The polygraphic recordings and corresponding hypnograms revealed that dieckol accelerated the initiation of non-rapid eye movement sleep (NREMS); it shortened sleep latency and increased NREMS duration. According to the change in time-course, dieckol showed sleep-enhancing effects by increasing the amount of NREMS and decreasing wakefulness during the same hours. Additionally, sleep quality was evaluated by analyzing the EEG power density, and dieckol was found to not affect sleep intensity while zolpidem was found to reduce it. Finally, we treated mice with zolpidem or dieckol in combination with flumazenil and found the latter to inhibit the sleep-enhancing effect of dieckol and zolpidem, thereby indicating that dieckol exerts sleep-enhancing effects by activating the GABA_A-BZD receptor, similar to zolpidem. These results implied that dieckol can be used as a promising herbal sleep aid with minimal side effects, unlike the existing hypnotics.

Assessment of antidepressant and sedative-hypnotic activities of methanolic crude extracts of Stephania japonica (Thunb.) Miers. whole plants

In this study, methanolic crude extracts of Stephania japonica (Thunb.) Miers. (MESJ) whole plants were examined for possible antidepressant and sedative-hypnotic activities. Herein, the forced swimming test and tail suspension test were conducted to explore the antidepressant activity. In addition, the open field test and hole-board test were performed to evaluate the sedative-hypnotic activities. In the acute toxicity test, the MESJ ensured safety up to a dose of 2000 mg/kg, p.o. The experimental doses were 100 and 200 mg/kg p.o. In both the forced swimming test and tail suspension test, the extract significantly (p<0.01 and p<0.05) inhibited immobility time in a dose dependent manner compared to the control. These results (13.56-26.46% inhibition) indicate the mild antidepressant activity of MESJ compared to nortriptyline (60.4-64.6% inhibition). The open field test and hole-board test demonstrated the dose dependent significant (p<0.001, p<0.01 and p<0.05) and moderate sedative-hypnotic activities of the extract compared to diazepam. However, these activities were found to gradually decrease after 60 min in the open field test and must be considered as short-term activities, compared to diazepam. It can be claimed that the methanolic crude extract of Stephania japonica possesses mild antidepressant and moderate but short-term sedative-hypnotic activities.

The effect of perioperative anesthetics for prevention of postoperative delirium on general anesthesia: A network meta-analysis

STUDY OBJECTIVE

Postoperative delirium (POD) is a common neurological system disorder in surgical patients. Anesthesia providers have a wide choice of sedative agents involving different mechanisms in clinical practice, and the incidence of POD varies regarding which sedative agent administered. This network meta-analysis aimed to comprehensively analyze the safety and efficacy of each choice for patients.

DESIGN

A network meta-analysis.

SETTING

Vanderbilt University Medical Center.

MEASUREMENTS

We searched PubMed, EMBASE, Ovid Medline and Cochrane Central Register of Controlled Trials (CENTRAL) through the end of September 2018 with the registration number CRD42018110585. The randomized controlled trials were identified and extracted by two reviewers independently. Commonly used sedative agents such as placebo, sevoflurane, desflurane, isoflurane, dexmedetomidine, propofol, midazolam, and ketamine were assessed in this network meta-analysis and the primary outcome was the incidence of POD. The data were synthesized by network meta-analysis. Pair-wise meta-analyses were conducted using the random-effects model. Each intervention was ranked according to its corresponding surface under the cumulative ranking curve (SUCRA) values. The GRADE framework was undertaken to evaluate the risk of bias.

MAIN RESULTS

We identified 39 RCTs and 5991 patients in this meta-analysis. Dexmedetomidine was found to be the most effective option in reducing POD, compared to midazolam, propofol, desflurane, and sevoflurane. The results revealed that dexmedetomidine was associated with a lower incidence of POD, whereas midazolam was associated with a significantly higher number of patients with delirium. Midazolam and propofol were also associated with a higher incidence of perioperative hypotension and bradycardia.

CONCLUSION

Our study provided meta-analytic evidence and suggested dexmedetomidine could be considered as the most effective sedative agent to reduce POD. However, clinical practitioners still need to weigh the pros and cons before choosing a sedative agent for individual patient.

Intra-"cortical" activity during avian non-REM and REM sleep: variant and invariant traits between birds and mammals

Several mammalian-based theories propose that the varying patterns of neuronal activity occurring in wakefulness and sleep reflect different modes of information processing. Neocortical slow-waves, hippocampal sharp-wave ripples, and thalamocortical spindles occurring during mammalian non-rapid eye-movement (NREM) sleep are proposed to play a role in systems-level memory consolidation. Birds show similar NREM and REM (rapid eye-movement) sleep stages to mammals; however, it is unclear whether all neurophysiological rhythms implicated in mammalian memory consolidation are also present. Moreover, it is unknown whether the propagation of slow-waves described in the mammalian neocortex occurs in the avian "cortex" during natural NREM sleep. We used a 32-channel silicon probe connected to a transmitter to make intracerebral recordings of the visual hyperpallium and thalamus in naturally sleeping pigeons (Columba livia). As in the mammalian neocortex, slow-waves during NREM sleep propagated through the hyperpallium. Propagation primarily occurred in the thalamic input layers of the hyperpallium, regions that also showed the greatest slow-wave activity (SWA). Spindles were not detected in both the visual hyperpallium, including regions receiving thalamic input, and thalamus, using a recording method that readily detects spindles in mammals. Interestingly, during REM sleep fast gamma bursts in the hyperpallium (when present) were restricted to the thalamic input layers. In addition, unlike mice, the decrease in SWA from NREM to REM sleep was the greatest in these layers. Taken together, these variant and invariant neurophysiological aspects of avian and mammalian sleep suggest that there may be associated mechanistic and functional similarities and differences between avian and mammalian sleep.

Miniature Untethered EEG Recorder Improves Advanced Neuroscience Methodologies

Rodent electroencephalography (EEG) in preclinical research is frequently conducted in behaving animals. However, the difficulty inherent in identifying EEG epochs associated with a particular behavior or cue is a significant obstacle to more efficient analysis. In this paper we highlight a new solution, using infrared event stamping to accurately synchronize EEG, recorded from superficial sites above the hippocampus and prefrontal cortex, with video motion tracking data in a transgenic Alzheimer's disease (AD) mouse model. Epochs capturing specific behaviors were automatically identified and extracted prior to further analysis. This was achieved by the novel design of an ultra-miniature wearable EEG recorder, the NAT-1 device, and its in-situ IR recording module. The device is described in detail, and its contribution to enabling new neuroscience is demonstrated.

Photopotentiation of the GABAA receptor with caged diazepam

As the inhibitory γ-aminobutyric acid-ergic (GABAergic) transmission has a pivotal role in the central nervous system (CNS) and defective forms of its synapses are associated with serious neurological disorders, numerous versions of caged GABA and, more recently, photoswitchable ligands have been developed to investigate such transmission. While the complementary nature of these probes is evident, the mechanisms by which the GABA receptors can be photocontrolled have not been fully exploited. In fact, the ultimate need for specificity is critical for the proper synaptic exploration. No caged allosteric modulators of the GABA_A receptor have been reported so far; to introduce such an investigational approach, we exploited the structural motifs of the benzodiazepinic scaffold to develop a photocaged version of diazepam (CD) that was tested on basolateral amygdala (BLa) pyramidal cells in mouse brain slices. CD is devoid of any intrinsic activity toward the GABA_A receptor before irradiation. Importantly, CD is a photoreleasable GABA_A receptor-positive allosteric modulator that offers a different probing mechanism compared to caged GABA and photoswitchable ligands. CD potentiates the inhibitory signaling by prolonging the decay time of postsynaptic GABAergic currents upon photoactivation. Additionally, no effect on presynaptic GABA release was recorded. We developed a photochemical technology to individually study the GABA_A receptor, which specifically expands the toolbox available to study GABAergic synapses.

GABA Receptors and the Pharmacology of Sleep

Current GABAergic sleep-promoting medications were developed pragmatically, without making use of the immense diversity of GABA_A receptors. Pharmacogenetic experiments are leading to an understanding of the circuit mechanisms in the hypothalamus by which zolpidem and similar compounds induce sleep at α2βγ2-type GABA_A receptors. Drugs acting at more selective receptor types, for example, at receptors containing the α2 and/or α3 subunits expressed in hypothalamic and brain stem areas, could in principle be useful as hypnotics/anxiolytics. A highly promising sleep-promoting drug, gaboxadol, which activates αβδ-type receptors failed in clinical trials. Thus, for the time being, drugs such as zolpidem, which work as positive allosteric modulators at GABA_A receptors, continue to be some of the most effective compounds to treat primary insomnia.

Effects of Diazepam on Low-Frequency and High-Frequency Electrocortical γ-Power Mediated by α1- and α2-GABAA Receptors

Patterns of spontaneous electric activity in the cerebral cortex change upon administration of benzodiazepines. Here we are testing the hypothesis that the prototypical benzodiazepine, diazepam, affects spectral power density in the low (20-50 Hz) and high (50-90 Hz) γ-band by targeting GABAA receptors harboring α1- and α2-subunits. Local field potentials (LFPs) and action potentials were recorded in the barrel cortex of wild type mice and two mutant strains in which the drug exclusively acted via GABAA receptors containing either α1- (DZα1-mice) or α2-subunits (DZα2-mice). In wild type mice, diazepam enhanced low γ-power. This effect was also evident in DZα2-mice, while diazepam decreased low γ-power in DZα1-mice. Diazepam increased correlated local LFP-activity in wild type animals and DZα2- but not in DZα1-mice. In all genotypes, spectral power density in the high γ-range and multi-unit action potential activity declined upon diazepam administration. We conclude that diazepam modifies low γ-power in opposing ways via α1- and α2-GABAA receptors. The drug's boosting effect involves α2-receptors and an increase in local intra-cortical synchrony. Furthermore, it is important to make a distinction between high- and low γ-power when evaluating the effects of drugs that target GABAA receptors.

Sleep Pharmacogenetics: The Promise of Precision Medicine

Pharmacogenetics is the branch of personalized medicine concerned with the variability in drug response occurring because of heredity. Advances in genetics research, and decreasing costs of gene sequencing, are promoting tremendous growth in pharmacogenetics in all areas of medicine, including sleep medicine. This article reviews the body of research indicating that there are genetic variations that affect the therapeutic actions and adverse effects of agents used for the treatment of sleep disorders to show the potential of pharmacogenetics to improve the clinical practice of sleep medicine.

A Standardized Phlorotannin Supplement Attenuates Caffeine-Induced Sleep Disruption in Mice

In our previous studies, a standardized phlorotannin (brown seaweed polyphenol) supplement (PS) exhibited sleep-promoting effects via type A γ-aminobutyric acid-benzodiazepine receptors in mice. In addition, in human clinical trials, it decreased wake after sleep onset in adults with sleep disturbance. In this follow-up study, we investigated whether PS attenuates caffeine-induced sleep disruption in mice. The effects of PS were evaluated in a caffeine model by analyzing sleep architecture based on electroencephalogram and electromyogram findings, and were compared with the effects of a well-known sedative-hypnotic drug zolpidem (ZPD). As expected, oral administration of caffeine (25 mg/kg) significantly increased sleep latency and decreased the amount of non-rapid eye movement sleep (NREMS). In the caffeine + PS and caffeine + ZPD groups, PS (500 mg/kg) attenuated caffeine-induced sleep disruption, and its effects were comparable with those of ZPD (10 mg/kg). In particular, PS inhibited the arousal effects of caffeine without change in delta activity during NREMS, whereas ZPD produced a decrease in the delta activity. Considering global trends in coffee and energy drink consumption, our finding suggest that PS may be useful to relieve transitory insomnia symptoms caused by caffeine consumption, unlike the prescription drug ZPD.

Clinical and Experimental Human Sleep-Wake Pharmacogenetics

Sleep and wakefulness are highly complex processes that are elegantly orchestrated by fine-tuned neurochemical changes among neuronal and non-neuronal ensembles, nuclei, and networks of the brain. Important neurotransmitters and neuromodulators regulating the circadian and homeostatic facets of sleep-wake physiology include melatonin, γ-aminobutyric acid, hypocretin, histamine, norepinephrine, serotonin, dopamine, and adenosine. Dysregulation of these neurochemical systems may cause sleep-wake disorders, which are commonly classified into insomnia disorder, parasomnias, circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, sleep-related movement disorders, and sleep-related breathing disorders. Sleep-wake disorders can have far-reaching consequences on physical, mental, and social well-being and health and, thus, need be treated with effective and rational therapies. Apart from behavioral (e.g., cognitive behavioral therapy for insomnia), physiological (e.g., chronotherapy with bright light), and mechanical (e.g., continuous positive airway pressure treatment of obstructive sleep apnea) interventions, pharmacological treatments often are the first-line clinical option to improve disturbed sleep and wake states. Nevertheless, not all patients respond to pharmacotherapy in uniform and beneficial fashion, partly due to genetic differences. The improved understanding of the neurochemical mechanisms regulating sleep and wakefulness and the mode of action of sleep-wake therapeutics has provided a conceptual framework, to search for functional genetic variants modifying individual drug response phenotypes. This article will summarize the currently known genetic polymorphisms that modulate drug sensitivity and exposure, to partly determine individual responses to sleep-wake pharmacotherapy. In addition, a pharmacogenetic strategy will be outlined how based upon classical and opto-/chemogenetic strategies in animals, as well as human genetic associations, circuit mechanisms regulating sleep-wake functions in humans can be identified. As such, experimental human sleep-wake pharmacogenetics forms a bridge spanning basic research and clinical medicine and constitutes an essential step for the search and development of novel sleep-wake targets and therapeutics.

Developmental seizures and mortality result from reducing GABAA receptor α2-subunit interaction with collybistin

Fast inhibitory synaptic transmission is mediated by γ-aminobutyric acid type A receptors (GABAARs) that are enriched at functionally diverse synapses via mechanisms that remain unclear. Using isothermal titration calorimetry and complementary methods we demonstrate an exclusive low micromolar binding of collybistin to the α2-subunit of GABAARs. To explore the biological relevance of collybistin-α2-subunit selectivity, we generate mice with a mutation in the α2-subunit-collybistin binding region (Gabra2-1). The mutation results in loss of a distinct subset of inhibitory synapses and decreased amplitude of inhibitory synaptic currents. Gabra2-1 mice have a striking phenotype characterized by increased susceptibility to seizures and early mortality. Surviving Gabra2-1 mice show anxiety and elevations in electroencephalogram δ power, which are ameliorated by treatment with the α2/α3-selective positive modulator, AZD7325. Taken together, our results demonstrate an α2-subunit selective binding of collybistin, which plays a key role in patterned brain activity, particularly during development.

GABAA receptor polymorphisms in alcohol use disorder in the GWAS era

Alcohol use disorder (AUD) is a chronic, relapsing, neuro-psychiatric illness of high prevalence and with a serious public health impact worldwide. It is complex and polygenic, with a heritability of about 50%, and influenced by environmental causal heterogeneity. Risk factors associated with its etiology have a genetic component. GABA (γ-aminobutyric acid) is a major inhibitory neurotransmitter in mammalian brain. GABA_A receptors are believed to mediate some of the physiological and behavioral actions of alcohol. In this critical review, relevant genetic terms and type and methodology of the genetic studies are briefly explained. Postulated candidate genes that encode subunits of GABA_A receptors, with all the reported SNPs, are presented. Genetic studies and meta-analyses examining polymorphisms of the GABA_A receptor and their association with AUD predisposition are presented. The data are critically examined with reference to recent GWAS studies that failed to show relations between GABA_A receptors and AUD. Restrictions and perspectives of the different findings are discussed.

Triphlorethol A, a Dietary Polyphenol from Seaweed, Decreases Sleep Latency and Increases Non-Rapid Eye Movement Sleep in Mice

In our previous studies, we have demonstrated that marine polyphenol phlorotannins promote sleep through the benzodiazepine site of the gamma-aminobutyric acid type A (GABA_A) receptors. In this follow-up study, the sleep-promoting effects of triphlorethol A, one of the major phlorotannin constituents, were investigated. The effect of triphlorethol A on sleep-wake architecture and profiles was evaluated based on electroencephalogram and electromyogram data from C57BL/6N mice and compared with the well-known hypnotic drug zolpidem. Oral administration of triphlorethol A (5, 10, 25, and 50 mg/kg) dose-dependently decreased sleep latency and increased sleep duration during pentobarbital-induced sleep in imprinting control region mice. Triphlorethol A (50 mg/kg) significantly decreased sleep latency and increased the amount of non-rapid eye movement sleep (NREMS) in C57BL/6N mice, without affecting rapid eye movement sleep (REMS). There was no significant difference between the effects of triphlorethol A at 50 mg/kg and zolpidem at 10 mg/kg. Triphlorethol A had no effect on delta activity (0.5–4 Hz) of NREMS, whereas zolpidem significantly decreased it. These results not only support the sleep-promoting effects of marine polyphenol phlorotannins, but also suggest that the marine polyphenol compound triphlorethol A is a promising structure for developing novel sedative hypnotics.

Detection of time-, frequency- and direction-resolved communication within brain networks

Electroencephalography (EEG) records fast-changing neuronal signalling and communication and thus can offer a deep understanding of cognitive processes. However, traditional data analyses which employ the Fast-Fourier Transform (FFT) have been of limited use as they do not allow time- and frequency-resolved tracking of brain activity and detection of directional connectivity. Here, we applied advanced qEEG tools using autoregressive (AR) modelling, alongside traditional approaches, to murine data sets from common research scenarios: (a) the effect of age on resting EEG; (b) drug actions on non-rapid eye movement (NREM) sleep EEG (pharmaco-EEG); and (c) dynamic EEG profiles during correct vs incorrect spontaneous alternation responses in the Y-maze. AR analyses of short data strips reliably detected age- and drug-induced spectral EEG changes, while renormalized partial directed coherence (rPDC) reported direction- and time-resolved connectivity dynamics in mice. Our approach allows for the first time inference of behaviour- and stage-dependent data in a time- and frequency-resolved manner, and offers insights into brain networks that underlie working memory processing beyond what can be achieved with traditional methods.

Sleep- and Wake-Like States in Small Networks In Vivo and In Vitro

Wakefulness and sleep are highly complex and heterogeneous processes, involving multiple neurotransmitter systems and a sophisticated interplay between global and local networks of neurons and non-neuronal cells. Macroscopic approaches applied at the level of the whole organism, view sleep as a global behaviour and allow for investigation into aspects such as the effects of insufficient or disrupted sleep on cognitive function, metabolism, thermoregulation and sensory processing. While significant progress has been achieved using such large-scale approaches, the inherent complexity of sleep-wake regulation has necessitated the development of methods which tackle specific aspects of sleep in isolation. One way this may be achieved is by investigating specific cellular or molecular phenomena in the whole organism in situ, either during spontaneous or induced sleep-wake states. This approach has greatly advanced our knowledge about the electrophysiology and pharmacology of ion channels, specific receptors, intracellular pathways and the small networks implicated in the control and regulation of the sleep-wake cycle. Importantly though, there are a variety of external and internal factors that influence global behavioural states which are difficult to control for using these approaches. For this reason, over the last few decades, ex vivo experimental models have become increasingly popular and have greatly advanced our understanding of many fundamental aspects of sleep, including the neuroanatomy and neurochemistry of sleep states, sleep regulation, the origin and dynamics of specific sleep oscillations, network homeostasis as well as the functional roles of sleep. This chapter will focus on the use of small neuronal networks as experimental models and will highlight the most significant and novel insights these approaches have provided.

A novel neurological function of rice bran: a standardized rice bran supplement promotes non-rapid eye movement sleep in mice through histamine H1 receptors

SCOPE

Although rice bran has been shown to be associated with a wide spectrum of health benefits, to date, there are no reports on its effects on sleep. We investigated the effect of rice bran on sleep and the mechanism underlying this effect.

METHODS AND RESULTS

Electroencephalography was used to evaluate the effects of standardized rice bran supplement (RBS) and doxepin hydrochloride (DH), a histamine H₁ receptor (H₁ R) antagonist used as a positive control, on sleep in mice. The mechanism of RBS action was investigated using knockout (KO) mice and ex vivo electrophysiological recordings. Oral administration of RBS and DH significantly decreased sleep latency and increased the amount of non-rapid eye movement sleep (NREMS) in mice. Similar to DH, RBS fully inhibited H₁ R agonist-induced increase in action potential frequency in tuberomammillary nucleus neurons. In H₁ R KO mice, neither RBS nor DH administration led to the increase in NREMS and decrease in sleep latency observed in WT mice. These results indicate that the sleep-promoting effect of RBS is completely dependent on H₁ R antagonism.

CONCLUSIONS

RBS decreases sleep latency and promotes NREMS through the inhibition of H₁ R, suggesting that it could be a promising therapeutic agent for insomnia.

Neuroligin 3 R451C mutation alters electroencephalography spectral activity in an animal model of autism spectrum disorders

Human studies demonstrate that sleep impairment is a concurrent comorbidity of autism spectrum disorders (ASD), but its etiology remains largely uncertain. One of the prominent theories of ASD suggests that an imbalance in synaptic excitation/inhibition may contribute to various aspects of ASD, including sleep impairments. Following the identification of Nlgn3^R451C mutation in patients with ASD, its effects on synaptic transmission and social behaviours have been examined extensively in the mouse model. However, the contributory role of this mutation to sleep impairments in ASD remains unknown. In this study, we showed that Nlgn3^R451C knock-in mice, an established genetic model for ASD, exhibited normal duration and distribution of sleep/wake states but significantly altered electroencephalography (EEG) power spectral profiles for wake and sleep.

Rosmarinic Acid Potentiates Pentobarbital-Induced Sleep Behaviors and Non-Rapid Eye Movement (NREM) Sleep through the Activation of GABAA-ergic Systems

It has been known that RA, one of major constituents of Perilla frutescens which has been used as a traditional folk remedy for sedation in oriental countries, shows the anxiolytic-like and sedative effects. This study was performed to know whether RA may enhance pentobarbital-induced sleep through γ-aminobutyric acid (GABA)_A-ergic systems in rodents. RA (0.5, 1.0 and 2.0 mg/ kg, p.o.) reduced the locomotor activity in mice. RA decreased sleep latency and increased the total sleep time in pentobarbital (42 mg/kg, i.p.)-induced sleeping mice. RA also increased sleeping time and number of falling sleep mice after treatment with sub-hypnotic pentobarbital (28 mg/kg, i.p.). In electroencephalogram (EEG) recording, RA (2.0 mg/kg) not only decreased the counts of sleep/wake cycles and REM sleep, but also increased the total and NREM sleep in rats. The power density of NREM sleep showed the increase in δ-waves and the decrease in α-waves. On the other hand, RA (0.1, 1.0 and 10 μg/ml) increased intracellular Cl^- influx in the primary cultured hypothalamic cells of rats. RA (p.o.) increased the protein expression of glutamic acid decarboxylase (GAD_65/67) and GABA_A receptors subunits except β1 subunit. In conclusion, RA augmented pentobarbital-induced sleeping behaviors through GABA_A-ergic transmission. Thus, it is suggested that RA may be useful for the treatment of insomnia.

Potentiation of decursinol angelate on pentobarbital-induced sleeping behaviors via the activation of GABAA-ergic systems in rodents

Angelicae Gigantis Radix (AGR, Angelica gigas) has been used for a long time as a traditional folk medicine in Korea and oriental countries. Decursinol angelate (DCA) is structurally isomeric decursin, one of the major components of AGR. This study was performed to confirm whether DCA augments pentobarbital-induced sleeping behaviors via the activation of GABA_A-ergic systems in animals. Oral administration of DCA (10, 25 and 50 mg/kg) markedly suppressed spontaneous locomotor activity. DCA also prolonged sleeping time, and decreased the sleep latency by pentobarbital (42 mg/kg), in a dose-dependent manner, similar to muscimol, both at the hypnotic (42 mg/kg) and sub-hypnotic (28 mg/kg) dosages. Especially, DCA increased the number of sleeping animals in the sub-hypnotic dosage. DCA (50 mg/kg, p.o.) itself modulated sleep architectures; DCA reduced the counts of sleep/wake cycles. At the same time, DCA increased total sleep time, but not non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. In the molecular experiments. DCA (0.001, 0.01 and 0.1 µg/ml) increased intracellular Cl- influx level in hypothalamic primary cultured neuronal cells of rats. In addition, DCA increased the protein expression of glutamic acid decarboxylase (GAD_65/67) and GABA_A receptors subtypes. Taken together, these results suggest that DCA potentiates pentobarbital-induced sleeping behaviors through the activation of GABA_A-ergic systems, and can be useful in the treatment of insomnia.

Tenuifolin, a saponin derived from Radix Polygalae, exhibits sleep-enhancing effects in mice

BACKGROUND

Radix Polygalae, the dried root of Polygala tenuifolia, has been extensively used as a traditional Chinese medicine for promoting intelligence and tranquilization. Polygalasaponins extracted from the root of P. tenuifolia possess evident anxiolytic and sedative-hypnotic activities. Previous studies have reported that tenuifolin was a major constituent of polygalasaponins.

PURPOSE

The currently study aims to investigate the hypnotic effect and possible mechanism of tenuifolin in freely moving mice.

DESIGN/METHODS

The hypnotic effects of tenuifolin (20, 40 and 80mg/kg, p.o.) were assessed by electroencephalographic (EEG) and electromyographic (EMG) analysis. Double-staining immunohistochemistry test was performed to evaluate the neuronal activity of sleep-wake regulating brain areas. High performance liquid chromatograph- electrochemical detection (HPLC-ECD) and ultrafast liquid chromatography-mass spectrometry (UFLC-MS) were used for the detection of neurotransmitters. Locomotor activity was measured by Open-field Test.

RESULTS

Tenuifolin at doses of 40 and 80mg/kg (p.o.) significantly prolonged the total sleep time by increasing the amount of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep, associated with the significant increase in the bouts of episodes respectively. After administration of tenuifolin, the cortical EEG power spectral densities during NREM and REM sleep were similar to that of natural sleep (vehicle) and thus compatible with physiological sleep. Double-immunohistochemistry staining test showed that tenuifolin increased the c-Fos positive ratios of GABAergic NREM sleep-promoting neurons in ventrolateral preoptic area (VLPO), cholinergic REM sleep-promoting neurons in laterodorsal tegmental area (LDT) and pontomesencephalic tegmental area (PPT) and decreased the c-Fos positive ratios in wake-promoting neurons (locus coeruleus (LC) and perifornical area (Pef)). Neurotransmitter detections revealed that tenuifolin significantly reduced the noradrenaline (NA) levels in LC, VLPO, PPT and LDT, elevated the GABA levels in VLPO, LC and Pef and increased the acetylcholine (Ach) levels in LDT and PPT. In addition, tenuifolin did not cause any change to locomotor activity.

CONCLUSION

Taken together, these results provide the first experimental evidence of the significant sleep-enhancing effect of tenuifolin in mice. This effect appears to be mediated, at least in part, by the activation of GABAergic systems and/or by the inhibition of noradrenergic systems. Moreover, this study adds new scientific evidence and highlights the therapeutic potential of the medicinal plant P. tenuifolia in the development of phytomedicines with hypnotic properties.

To what extent is it possible to dissociate the anxiolytic and sedative/hypnotic properties of GABAA receptors modulators?

The relatively common view indicates a possible dissociation between the anxiolytic and sedative/hypnotic properties of benzodiazepines (BZs). Indeed, GABAA receptor (GABAAR) subtypes have specific cerebral distribution in distinct neural circuits. Thus, GABAAR subtype-selective drugs may be expected to perform distinct functions. However, standard behavioral test assays provide limited direction towards highlighting new action mechanisms of ligands targeting GABAARs. Automated behavioral tests, lack sensitivity as some behavioral characteristics or subtle behavioral changes of drug effects or that are not considered in the overall analysis (Ohl et al., 2001) and observation-based analyses are not always performed. In addition, despite the use of genetically engineered mice, any possible dissociation between the anxiolytic and sedative properties of BZs remains controversial. Moreover, the involvement the different subtypes of GABAAR subtypes in the anxious behavior and the mechanism of action of anxiolytic agents remains unclear since there has been little success in the pharmacological investigations so far. This raises the question of the involvement of the different subunits in anxiolytic-like and/or sedative effects; and the actual implication of these subunits, particularly, α-subunits in the modulation of sedation and/or anxiety-related disorders. This present review was prompted by several conflicting studies on the degree of involvement of these subunits in anxiolytic-like and/or sedative effects. To this end, we explored the GABAergic system, particularly, the role of different subunits containing synaptic GABAARs. We report herein the targeting gene encoding the different subunits and their contribution in anxiolytic-like and/or sedative actions, as well as, the mechanism underlying tolerance to BZs.

α-Pinene, a Major Constituent of Pine Tree Oils, Enhances Non-Rapid Eye Movement Sleep in Mice through GABAA-benzodiazepine Receptors

α-Pinene is a major monoterpene of the pine tree essential oils. It has been reported that α-pinene shows anxiolytic and hypnotic effects upon inhaled administration. However, hypnotic effect by oral supplementation and the molecular mechanism of α-pinene have not been determined yet. By combining in vivo sleep behavior, ex vivo electrophysiological recording from brain slices, and in silico molecular modeling, we demonstrate that (-)-α-pinene shows sleep enhancing property through a direct binding to GABAA-benzodiazepine (BZD) receptors by acting as a partial modulator at the BZD binding site. The effect of (-)-α-pinene on sleep-wake profiles was evaluated by recording electroencephalogram and electromyogram. The molecular mechanism of (-)-α-pinene was investigated by electrophysiology and molecular docking study. (-)-α-pinene significantly increased the duration of non-rapid eye movement sleep (NREMS) and reduced the sleep latency by oral administration without affecting duration of rapid eye movement sleep and delta activity. (-)-α-pinene potentiated the GABAA receptor-mediated synaptic response by increasing the decay time constant of sIPSCs in hippocampal CA1 pyramidal neurons. These effects of (-)-α-pinene on sleep and inhibitory synaptic response were mimicked by zolpidem, acting as a modulator for GABAA-BZD receptors, and fully antagonized by flumazenil, an antagonist for GABAA-BZD receptor. (-)-α-pinene was found to bind to aromatic residues of α1- and -γ2 subunits of GABAA-BZD receptors in the molecular model. We conclude that (-)-α-pinene enhances the quantity of NREMS without affecting the intensity of NREMS by prolonging GABAergic synaptic transmission, acting as a partial modulator of GABAA-BZD receptors and directly binding to the BZD binding site of GABAA receptor.

Hydroalcoholic extract of Myrtus communis can alter anxiety and sleep parameters: a behavioural and EEG sleep pattern study in mice and rats

CONTEXT

Myrtus communis L. (Myrtaceae), myrtle, is an evergreen shrub with strong antibacterial, anti-inflammatory, antihyperglycemic and antioxidant activities. Also, it is used as a sedative-hypnotic plant in Iranian traditional medicine.

OBJECTIVE

This study evaluates the effect of 80% ethanolic extract of M. communis leaves on sleep and anxiety in mice and rats.

MATERIALS AND METHODS

Male NMRI mice were subjected to open field, righting reflex, grip strength and pentylentetrazole-induced seizure tests. Male Wistar rats were used to evaluate the alterations in rapid eye movement (REM) and non-REM (NREM) sleep. They were treated with 25-400 mg/kg doses of the extract intraperitoneally.

RESULTS

The applied doses (50-200 mg/kg) of M. communis extract increased vertical (ED50 = 40.2 ± 6.6 mg/kg) and vertical and horizontal activity (ED50 = 251 ± 55 mg/kg), while treatment with 200 and 400 mg/kg attenuated muscle tone significantly compared to vehicle treated animals (p < 0.001 for all) in a dose-independent manner. Also, a significant hypnotic and not anticonvulsant effect was observed when animals were treated with 200 mg/kg of the extract (p < 0.01). In this regard, electroencephalography results showed that REM sleep time was decreased (2.4 ± 0.5%), while total and NREM sleep times were increased significantly compared to the control group of mice (82.5 ± 7.6%).

DISCUSSION AND CONCLUSION

The data show the anxiolytic and muscle relaxant effect of the extract without anticonvulsant activities. The anxiolytic, myorelaxant and hypnotic effects without effect on seizure threshold are in line with the effect of a alpha 2 GABA receptor agonist.

Oral administration of Japanese sake yeast (Saccharomyces cerevisiae sake) promotes non-rapid eye movement sleep in mice via adenosine A2A receptors

We have demonstrated previously that Japanese sake yeast improves sleep quality in humans. In the present study, we examined the molecular mechanisms of sake yeast to induce sleep by monitoring locomotor activity, electromyogram and electroencephalogram in mice. Oral administration of Japanese sake yeast (100, 200, and 300 mg kg^-1 ) decreased the locomotor activity by 18, 46 and 59% and increased the amount of non-rapid eye movement (NREM) sleep by 1.5-, 2.3- and 2.4-fold (to 37 ± 6, 57 ± 8, and 60 ± 4 min from 25 ± 6 min in the vehicle-administered group, respectively) in a dose-dependent manner for 4 h after oral administration. However, Japanese sake yeast did not change the amount of rapid eye movement (REM) sleep, the electroencephalogram power density during NREM sleep or show any adverse effects, such as rebound of insomnia, during 24 h postadministration and on the next day. An intraperitoneal pretreatment with an adenosine A_2A receptor-selective antagonist, ZM241385 (15 mg kg^-1 ), reduced the amount of NREM sleep of sake yeast-administered mice to the basal level, without changing basal amount of sleep. Conversely, an A₁ receptor-selective antagonist, 8-cyclopentyltheophylline (10 mg kg^-1 ), did not affect the sleep-promoting effect of Japanese sake yeast. Thus, Japanese sake yeast promotes NREM sleep via activation of adenosine A_2A but not A₁ receptors.

Paeoniflorin Promotes Non-rapid Eye Movement Sleep via Adenosine A1 Receptors

Paeoniflorin (PF, C23H28O11), one of the principal active ingredients of Paeonia Radix, exerts depressant effects on the central nervous system. We determined whether PF could modulate sleep behaviors and the mechanisms involved. Electroencephalogram and electromyogram recordings in mice showed that intraperitoneal PF administered at a dose of 25 or 50 mg/kg significantly shortened the sleep latency and increased the amount of non-rapid eye movement (NREM). Immunohistochemical study revealed that PF decreased c-fos expression in the histaminergic tuberomammillary nucleus (TMN). The sleep-promoting effects and changes in c-fos induced by PF were reversed by 8-cyclopentyl-1,3-dimethylxanthine (CPT), an adenosine A1 receptor antagonist, and PF-induced sleep was not observed in adenosine A1 receptor knockout mice. Whole-cell patch clamping in mouse brain slices showed that PF significantly decreased the firing frequency of histaminergic neurons in TMN, which could be completely blocked by CPT. These results indicate that PF increased NREM sleep by inhibiting the histaminergic system via A1 receptors.