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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 -
Frontiers in Cellular Neuroscience 2018GABA receptors (GABARs) play a crucial inhibitory role in the CNS. Benzodiazepines (BDZs) are positive modulators of specific subtypes of GABARs, but the underlying...
GABA receptors (GABARs) play a crucial inhibitory role in the CNS. Benzodiazepines (BDZs) are positive modulators of specific subtypes of GABARs, but the underlying mechanism remains obscure. Early studies demonstrated the major impact of BDZs on binding and more recent investigations indicated gating, but it is unclear which transitions are affected. Moreover, the upregulation of GABAR spontaneous activity by BDZs indicates their impact on receptor gating but the underlying mechanisms remain unknown. Herein, we investigated the effect of a BDZ (flurazepam) on the spontaneous and GABA-induced activity for wild-type (WT, αβγ) and mutated (at the orthosteric binding site αF64) GABARs. Surprisingly, in spite of the localization at the binding site, these mutations increased the spontaneous activity. Flurazepam (FLU) upregulated this activity for mutants and WT receptors to a similar extent by affecting opening/closing transitions. Spontaneous activity affected GABA-evoked currents and is manifested as an overshoot after agonist removal that depended on the modulation by BDZs. We explain the mechanism of this phenomenon as a cross-desensitization of ligand-activated and spontaneously active receptors. Moreover, due to spontaneous activity, FLU-pretreatment and co-application (agonist + FLU) protocols yielded distinct results. We provide also the first evidence that GABAR may enter the desensitized state in the absence of GABA in a FLU-dependent manner. Based on our data and model simulations, we propose that FLU affects agonist-induced gating by modifying primarily preactivation and desensitization. We conclude that the mechanisms of modulation of spontaneous and ligand-activated GABAR activity concerns gating but distinct transitions are affected in spontaneous and agonist-evoked activity.
PubMed: 30210295
DOI: 10.3389/fncel.2018.00237 -
BMJ Clinical Evidence Oct 2007Up to 40% of adults have insomnia, with difficulty getting to sleep, early waking, or feeling unrefreshed on waking. The prevalence of insomnia increases with age. Other... (Review)
Review
INTRODUCTION
Up to 40% of adults have insomnia, with difficulty getting to sleep, early waking, or feeling unrefreshed on waking. The prevalence of insomnia increases with age. Other risk factors include psychological factors, stress, daytime napping, and hyperarousal.
METHODS AND OUTCOMES
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of non-drug treatments for insomnia in elderly people? What are the effects of drug treatments for insomnia in elderly people? We searched: Medline, Embase, The Cochrane Library and other important databases up to October 2006 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
RESULTS
We found 28 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
CONCLUSIONS
In this systematic review we present information relating to the effectiveness and safety of the following interventions: benzodiazepines (brotizolam, flurazepam, loprazolam, midazolam, nitrazepam, quazepam, temazepam, and triazolam), cognitive behavioural therapy, diphenhydramine, exercise programmes, timed exposure to bright light, zaleplon, zolpidem, and zopiclone.
Topics: Aged; Cognitive Behavioral Therapy; Flurazepam; Humans; Risk Factors; Sleep; Sleep Initiation and Maintenance Disorders; Temazepam
PubMed: 19450355
DOI: No ID Found -
IARC Monographs on the Evaluation of... 1996
Review
Topics: Animals; Anti-Anxiety Agents; Anticonvulsants; Benzodiazepines; Carcinogenicity Tests; Carcinogens; Flurazepam; Humans
PubMed: 9097119
DOI: No ID Found -
British Journal of Clinical Pharmacology 19791 The effect of temazepam 15 and 30 mg, flurazepam 15 and 30 mg, quinalbarbitone 100 and 200 mg and placebo were studied in 14 healthy male volunteers according to a... (Clinical Trial)
Clinical Trial
1 The effect of temazepam 15 and 30 mg, flurazepam 15 and 30 mg, quinalbarbitone 100 and 200 mg and placebo were studied in 14 healthy male volunteers according to a Latin-square design. At 14-d intervals subjects received capsules 30 min before bedtime on 2 consecutive nights and were evaluated for objective sleep characteristics, for morning estimates of sleep characteristics, and for cognitive and psychomotive performance and subjective state at 3.5, 10.0 and 22.5 h after ingestion. 2 Changes in sleep induction and sleep maintenance were observed with temazepam 30 mg and flurazepam 30 mg had the greater effect on cognitive performance, whereas quinalbarbitone 20 mg had the greater effect on psychomotive performance. Subjective assessments of alertness were most affected by flurazepam, and by quinalbarbitone 200 mg. 4 The results suggest that temazepam produces less residual effects and is shorter acting than quinalbarbitone and flurazepam.
Topics: Adult; Anti-Anxiety Agents; Cognition; Emotions; Flurazepam; Humans; Male; Memory; Motor Skills; Secobarbital; Sleep; Sleep, REM; Temazepam
PubMed: 41542
DOI: 10.1111/j.1365-2125.1979.tb00456.x