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Nature Oct 2023Type A γ-aminobutyric acid receptors (GABARs) are the principal inhibitory receptors in the brain and the target of a wide range of clinical agents, including...
Type A γ-aminobutyric acid receptors (GABARs) are the principal inhibitory receptors in the brain and the target of a wide range of clinical agents, including anaesthetics, sedatives, hypnotics and antidepressants. However, our understanding of GABAR pharmacology has been hindered by the vast number of pentameric assemblies that can be derived from 19 different subunits and the lack of structural knowledge of clinically relevant receptors. Here, we isolate native murine GABAR assemblies containing the widely expressed α1 subunit and elucidate their structures in complex with drugs used to treat insomnia (zolpidem (ZOL) and flurazepam) and postpartum depression (the neurosteroid allopregnanolone (APG)). Using cryo-electron microscopy (cryo-EM) analysis and single-molecule photobleaching experiments, we uncover three major structural populations in the brain: the canonical α1β2γ2 receptor containing two α1 subunits, and two assemblies containing one α1 and either an α2 or α3 subunit, in which the single α1-containing receptors feature a more compact arrangement between the transmembrane and extracellular domains. Interestingly, APG is bound at the transmembrane α/β subunit interface, even when not added to the sample, revealing an important role for endogenous neurosteroids in modulating native GABARs. Together with structurally engaged lipids, neurosteroids produce global conformational changes throughout the receptor that modify the ion channel pore and the binding sites for GABA and insomnia medications. Our data reveal the major α1-containing GABAR assemblies, bound with endogenous neurosteroid, thus defining a structural landscape from which subtype-specific drugs can be developed.
Topics: Animals; Mice; Binding Sites; Cryoelectron Microscopy; Depression, Postpartum; Flurazepam; gamma-Aminobutyric Acid; Hypnotics and Sedatives; Ion Channel Gating; Neurosteroids; Photobleaching; Pregnanolone; Protein Conformation; Protein Subunits; Receptors, GABA-A; Sleep Initiation and Maintenance Disorders; Zolpidem
PubMed: 37730991
DOI: 10.1038/s41586-023-06556-w -
BioRxiv : the Preprint Server For... Feb 2023Type A GABA receptors (GABA Rs) are the principal inhibitory receptors in the brain and the target of a wide range of clinical agents, including anesthetics, sedatives,...
Type A GABA receptors (GABA Rs) are the principal inhibitory receptors in the brain and the target of a wide range of clinical agents, including anesthetics, sedatives, hypnotics, and antidepressants. However, our understanding of GABA R pharmacology has been hindered by the vast number of pentameric assemblies that can be derived from a total 19 different subunits and the lack of structural knowledge of clinically relevant receptors. Here, we isolate native murine GABA R assemblies containing the widely expressed α subunit, and elucidate their structures in complex with drugs used to treat insomnia (zolpidem and flurazepam) and postpartum depression (the neurosteroid allopregnanolone). Using cryo-EM analysis and single-molecule photobleaching experiments, we uncover only three structural populations in the brain: the canonical α β2γ receptor containing two α subunits and two unanticipated assemblies containing one α and either an α , α or α subunit. Both of the noncanonical assemblies feature a more compact arrangement between the transmembrane and extracellular domains. Interestingly, allopregnanolone is bound at the transmembrane α/β subunit interface, even when not added to the sample, revealing an important role for endogenous neurosteroids in modulating native GABA Rs. Together with structurally engaged lipids, neurosteroids produce global conformational changes throughout the receptor that modify both the pore diameter and binding environments for GABA and insomnia medications. Together, our data reveal that GABA R assembly is a strictly regulated process that yields a small number of structurally distinct complexes, defining a structural landscape from which subtype-specific drugs can be developed.
PubMed: 36824901
DOI: 10.1101/2023.02.16.528867 -
British Journal of Pharmacology Dec 2021In addition to binding to the classical high-affinity extracellular benzodiazepine binding site of the GABA receptor, some benzodiazepines occupy transmembrane...
BACKGROUND AND PURPOSE
In addition to binding to the classical high-affinity extracellular benzodiazepine binding site of the GABA receptor, some benzodiazepines occupy transmembrane inter-subunit anaesthetic sites that bind etomidate (β /α sites) or the barbiturate derivative R-mTFD-MPAB (α /β and γ /β sites). We aimed to define the functional effects of these interactions on GABA receptor activity and animal behaviour.
EXPERIMENTAL APPROACH
With flumazenil blocking classical high-affinity extracellular benzodiazepine site effects, modulation of GABA-activated currents by diazepam, midazolam and flurazepam was measured electrophysiologically in wildtype and M2-15' mutant α β γ GABA receptors. Zebrafish locomotive activity was also assessed in the presence of each benzodiazepine plus flumazenil.
KEY RESULTS
In the presence of flumazenil, micromolar concentrations of diazepam and midazolam both potentiated and inhibited wildtype GABA receptor currents. β N265M (M2-15' in the β /α sites) and α S270I (M2-15' in the α /β site) mutations reduced or abolished potentiation by these drugs. In contrast, the γ S280W mutation (M2-15' in the γ /β site) abolished inhibition. Flurazepam plus flumazenil only inhibited wildtype receptor currents, an effect unaltered by M2-15' mutations. In the presence of flumazenil, zebrafish locomotion was enhanced by diazepam at concentrations up to 30 μM and suppressed at 100 μM, suppressed by midazolam and enhanced by flurazepam.
CONCLUSIONS AND IMPLICATIONS
Benzodiazepine binding to transmembrane anaesthetic binding sites of the GABA receptor can produce positive or negative modulation manifesting as decreases or increases in locomotion, respectively. Selectivity for these sites may contribute to the distinct GABA receptor and behavioural actions of different benzodiazepines, particularly at high (i.e. anaesthetic) concentrations.
Topics: Animals; Anesthetics; Benzodiazepines; Binding Sites; Flumazenil; Receptors, GABA-A; Zebrafish
PubMed: 34386973
DOI: 10.1111/bph.15662 -
Open Access Macedonian Journal of... Sep 2019Insomnia is a symptom complex that comprises difficulties falling asleep, staying asleep or non-refreshing sleep in combination with daytime dysfunction or distress....
BACKGROUND
Insomnia is a symptom complex that comprises difficulties falling asleep, staying asleep or non-refreshing sleep in combination with daytime dysfunction or distress. Most people experience insomnia at some time during their lives. Because of its high incidence, and also because its symptoms are usually mild and transient, the importance of insomnia is frequently underestimated. Various conditions are associated with insomnia and can contribute to its development. They can be related to neurological or psychiatric disorders, which in turn may be aggravated by a deficiency of restorative sleep and daytime fatigue.
AIM
In this study, the authors compare the hypnotically effect of Flurazepam and Zolpidem applied on psychiatric cases treated in the Mental Health Centre "Prolet" in Skopje, Republic of Macedonia.
METHODS
The investigation covers 45 patients who have insomnia, in addition to their primary mental illness. The examination took six weeks, and it was divided into 3 equal phases. In the first phase of three weeks, Zolpidem was used, and in the third phases, Flurazepam was administrated. We used a self-estimating scale of 13 items and methods of global clinical estimation in the evaluation of received effects.
RESULTS
The results show that referring to the induction of the sleeping period, its duration and quality and the number of awakenings, there are no significant differences between the two medicaments used, but there was a significant difference between hypnotic medicaments and placebo.
CONCLUSION
The termination with the therapy, didn`t lead to the appearance of abstinential symptoms.
PubMed: 31844437
DOI: 10.3889/oamjms.2019.711 -
Psychiatria Danubina 2022To assess potential benefits of quetiapine for persistent sleep disturbances in patients with posttraumatic stress disorder (PTSD) on stable combined SSRI and...
Quetiapine Add-On Therapy May Improve Persistent Sleep Disturbances in Patients with PTSD on Stabile Combined SSRI and Benzodiazepine Combination: A One-Group Pretest-Posttest Study.
BACKGROUND
To assess potential benefits of quetiapine for persistent sleep disturbances in patients with posttraumatic stress disorder (PTSD) on stable combined SSRI and benzodiazepine therapy, who previously failed to respond to various benzodiazepine and non-benzodiazepine hypnotic adjuvant treatment as well as to first-generation antipsychotic add-on treatment.
SUBJECTS AND METHODS
Fifty-two male PTSD outpatients on stable combination treatment with SSRI and benzodiazepines, with persistent sleep disturbances not responding to prescription of zolpidem, flurazepam, nitrazepam, promazine, and levopromazine, were assessed for sleep disturbances improvements after prescription of quetiapine in the evening. Each patient met both ICD-10 and DSM-IV criteria for PTSD. Psychiatric comorbidity and premorbidity were excluded using the Mini-International Neuropsychiatric Interview (MINI). Improvement on the CAPS recurrent distressing dream item, reduction in the amount of time needed to fall asleep, prolongation of sleep duration, and reduction in average number of arousals per night in the last 7 days before the assessment period were used as efficacy measures.
RESULTS
All sleep-related parameters improved significantly at the end of a five-week follow-up: sleep duration increased by one hour (p<0.001), sleep latency decreased by 52.5 minutes (p<0.001), median number of arousals per night decreased from two to one (p<0.001), CAPS recurrent distressing dream item median decreased from five to four (p<0.001), and the number of patients dissatisfied with their sleep quality and quantity decreased from 45 to two (p<0.001).
CONCLUSION
Quetiapine prescribed in the evening may be successful therapy for persistent sleep disturbances in patients with PTSD and generally good response to an SSRI and benzodiazepine combination, who previously failed to respond to some of the usual hypnotic medication or addition of first-generation antipsychotics: zolpidem, flurazepam, nitrazepam, promazine, and levopromazine.
Topics: Antipsychotic Agents; Benzodiazepines; Flurazepam; Humans; Hypnotics and Sedatives; Male; Methotrimeprazine; Nitrazepam; Promazine; Quetiapine Fumarate; Sleep; Sleep Wake Disorders; Stress Disorders, Post-Traumatic; Zolpidem
PubMed: 35772134
DOI: 10.24869/psyd.2022.245 -
Sleep Advances : a Journal of the Sleep... 2021To evaluate effects of lemborexant (LEM), a dual orexin receptor antagonist, on next-morning sleep propensity assessed by a modified Multiple Sleep Latency Test (M-MSLT)...
OBJECTIVE
To evaluate effects of lemborexant (LEM), a dual orexin receptor antagonist, on next-morning sleep propensity assessed by a modified Multiple Sleep Latency Test (M-MSLT) in adults with insomnia disorder.
METHODS
Study 107 (E2006-A001-107) was a phase 1, randomized, double-blind, four-period crossover study. Subjects ( = 69) received oral single-dose placebo, LEM 5 mg (LEM5), and LEM 10 mg (LEM10) at bedtime in periods 1-3 in a randomized crossover and open-label flurazepam 30 mg in period 4. After an 8-hour overnight sleep opportunity, the M-MSLT measured average sleep onset latency (SOL). Mean change from baseline in average SOL versus placebo of -6.0 min or more was considered clinically meaningful. Other sleep propensity assessments included the proportion of subjects with average SOL >6 min shorter than placebo. LEM plasma concentrations, safety, and tolerability were also assessed.
RESULTS
M-MSLT assay sensitivity was confirmed by a clinically meaningful decrease in average SOL with flurazepam versus placebo (least squares mean [LSM] difference -6.06 min; 1-sided < 0.0001). In contrast, decreases in average SOL with LEM5 (LSM difference vs. placebo -1.15 min; 1-sided = 0.0262) and LEM10 (-3.48 min; < 0.0001) did not meet the predefined threshold for a clinically meaningful effect (LEM5, -2.12; LEM10, -4.46). Some individuals did experience higher sleep propensity (average SOL >6.0 min shorter than placebo), particularly with LEM10 (LEM10, 29.4%; LEM5, 13.2%).
CONCLUSIONS
In contrast to flurazepam, LEM5 and LEM10 did not show clinically meaningful mean increases in next-morning sleep propensity versus placebo. The possibility that some subjects may experience residual morning effects cannot be excluded. ClinicalTrials.gov, NCT02350309.
PubMed: 37193566
DOI: 10.1093/sleepadvances/zpab011