The mechanism of action of zopiclone

SummaryThe mechanism of action of the cyclopyrrolone hypnotic drug zopiclone involves allosteric modulation of the GABAA receptor. Zopiclone displaces the binding of [3H]-flunitrazepam with an affinity of 28 nM, and enhances the binding of the channel blocker [35S]-TBPS. The binding of zopiclone, unlike that of hypnotic benzodiazepines, is not facilitated by GABA. Zopiclone does not distinguish between GABAA receptors containing different α-subunits (BZ1 and BZ2 phenotype). Studies with protein-modifying agents (eg diethylpyrocarbonate) and photoaffinity labelling suggest that cyclopyrrolones bind to a domain on the GABAA receptor different from the benzodiazepine binding domain. The consequence of this interaction with the GABAA receptor is to potentiate responses to GABA, as can be demonstrated by electrophysiological methods. Subchronic treatment of mice with high doses of zopiclone does not produce the changes in sensitivity of the GABAA receptor that are observed with hypnotic benzodiazepines.

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Prevalence between different α subunits performing the benzodiazepine binding sites in native heterologous GABAA receptors containing the α2 subunit

Journal of Neurochemistry ◽

10.1046/j.1471-4159.2001.00551.x ◽

2008 ◽

Vol 79 (1) ◽

pp. 183-191 ◽

Cited By ~ 15

Author(s):

Juan Carlos del Río ◽

Francisco Araujo ◽

Blanca Ramos ◽

Diego Ruano ◽

Javier Vitorica

Keyword(s):

Gabaa Receptors ◽

Binding Sites ◽

Benzodiazepine Binding ◽

Benzodiazepine Binding Sites ◽

Α Subunits

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Competitive Antagonism of Etomidate Action by Diazepam

Anesthesiology ◽

10.1097/aln.0000000000003403 ◽

2020 ◽

Vol 133 (3) ◽

pp. 583-594 ◽

Cited By ~ 1

Author(s):

Megan McGrath ◽

Helen Hoyt ◽

Andrea Pence ◽

Selwyn S. Jayakar ◽

Xiaojuan Zhou ◽

...

Keyword(s):

Binding Site ◽

Gabaa Receptor ◽

Gabaa Receptors ◽

Response Curve ◽

Photoaffinity Labeling ◽

Peak Current ◽

Benzodiazepine Binding ◽

Concentration Response Curve

Background Recent cryo-electron microscopic imaging studies have shown that in addition to binding to the classical extracellular benzodiazepine binding site of the α1β3γ2L γ-aminobutyric acid type A (GABAA) receptor, diazepam also binds to etomidate binding sites located in the transmembrane receptor domain. Because such binding is characterized by low modulatory efficacy, the authors hypothesized that diazepam would act in vitro and in vivo as a competitive etomidate antagonist. Methods The concentration-dependent actions of diazepam on 20 µM etomidate-activated and 6 µM GABA-activated currents were defined (in the absence and presence of flumazenil) in oocyte-expressed α1β3γ2L GABAA receptors using voltage clamp electrophysiology. The ability of diazepam to inhibit receptor labeling of purified α1β3γ2L GABAA receptors by 3[H]azietomidate was assessed in photoaffinity labeling protection studies. The impact of diazepam (in the absence and presence of flumazenil) on the anesthetic potencies of etomidate and ketamine was compared in a zebrafish model. Results At nanomolar concentrations, diazepam comparably potentiated etomidate-activated and GABA-activated GABAA receptor peak current amplitudes in a flumazenil-reversible manner. The half-maximal potentiating concentrations were 39 nM (95% CI, 27 to 55 nM) and 26 nM (95% CI, 16 to 41 nM), respectively. However, at micromolar concentrations, diazepam reduced etomidate-activated, but not GABA-activated, GABAA receptor peak current amplitudes in a concentration-dependent manner with a half-maximal inhibitory concentration of 9.6 µM (95% CI, 7.6 to 12 µM). Diazepam (12.5 to 50 µM) also right-shifted the etomidate-concentration response curve for direct activation without reducing the maximal response and inhibited receptor photoaffinity labeling by 3[H]azietomidate. When administered with flumazenil, 50 µM diazepam shifted the etomidate (but not the ketamine) concentration–response curve for anesthesia rightward, increasing the etomidate EC50 by 18-fold. Conclusions At micromolar concentrations and in the presence of flumazenil to inhibit allosteric modulation via the classical benzodiazepine binding site of the GABAA receptor, diazepam acts as an in vitro and in vivo competitive etomidate antagonist. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New

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Symptomatic and Disease-Modifying Effects of GABAA Receptor Positive Allosteric Modulation in a Mouse Model of Chronic Stress

10.1101/2021.03.22.436517 ◽

2021 ◽

Author(s):

Ashley Bernardo ◽

Philippe Lee ◽

Michael Marcotte ◽

Yeunus Mian ◽

Zubair A. Khan ◽

...

Keyword(s):

Side Effects ◽

Gabaa Receptor ◽

Chronic Stress ◽

Gabaa Receptors ◽

Brain Regions ◽

Allosteric Modulation ◽

Neuronal Morphology ◽

Racemic Mixture ◽

Spine Density ◽

Α1 Subunit

AbstractChronic stress is a major risk factor for developing depressive disorders and animal models of stress recapitulate behavioral, cellular and molecular changes that are observed in human depression. Individuals exposed to chronic stress, or patients with MDD experience mood and cognitive dysfunctions. This is in part due to neuronal shrinkage in brain regions involved in several cognitive functions such as the prefrontal cortex (PFC) and the hippocampus (HPC). Also in the context of depression and chronic stress, expression levels and function of the main inhibitory neurotransmitter GABA are reduced. Thus far, drugs targeting this GABA deficit have failed to produce beneficial effects due to broad activity at various GABA receptor subunits, including the α1-subunit, resulting in broad side effects. However, refined and selective activity at the α2/3/5-subunit is hypothesized to exert beneficial effect, devoid of side effects.Here, we show that GL-II-73 and GL-I-54 exert positive allosteric modulation at the α5, and α2/3/5-contianing GABAA receptors respectively, and that they are effective both independently and in combination. Using unpredictable chronic mild stress (UCMS) experiments in male and female C57BL/6 mice (n=12 per group), we showed that acute and chronic administration of a GL-II-73/GL-I-54 racemic mixture (termed “GL-RM”) reduced anxiety-like phenotypes and reversed a working memory deficit in UCMS exposed mice. Brains from animals receiving chronic treatment were collected and stained using a Golgi staining technique. Using stereological approaches, neuronal morphology was reconstructed and dendritic length, spine count and spine density were assessed in pyramidal neurons of the PFC and hippocampus. Chronic GL-RM rescued spine density depletions caused by UCMS at apical and basal dendrites (PFC and CA1). Interestingly, spine densities in both brain regions were correlated to cognitive performance, confirming ameliorative benefits of GL-RM.Together, results support the value of selectively targeting GABAA receptors, excluding the α1-subunit, to overcome chronic stress-induced mood symptoms and cognitive deficits, as well as detriments in neuronal morphology. This study confirm results that were observed in old mice, using a α5-selective positive allosteric modulator, and reinforce the concept that the α2/3/5-containing GABAA receptor are suitable targets for the treatment of stress-induced disorders.

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Modest reduction of benzodiazepine binding in rat brain in vivo induced by antisense oligonucleotide to GABAA receptor γ2 subunit subtype

European Journal of Pharmacology Molecular Pharmacology ◽

10.1016/0922-4106(95)90088-8 ◽

1995 ◽

Vol 291 (3) ◽

pp. 439-441 ◽

Cited By ~ 11

Author(s):

Jesper Karle ◽

Mogens Nielsen

Keyword(s):

Rat Brain ◽

Gabaa Receptor ◽

Antisense Oligonucleotide ◽

Benzodiazepine Binding ◽

Modest Reduction

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Characterization in Rats of the Anxiolytic Potential of ELB139 [1-(4-Chlorophenyl)-4-piperidin-1-yl-1,5-dihydro-imidazol-2-on], a New Agonist at the Benzodiazepine Binding Site of the GABAA Receptor

Journal of Pharmacology and Experimental Therapeutics ◽

10.1124/jpet.105.084681 ◽

2005 ◽

Vol 314 (2) ◽

pp. 717-724 ◽

Cited By ~ 33

Author(s):

Barbara Langen ◽

Ute Egerland ◽

Katrin Bernöster ◽

Rita Dost ◽

Klaus Unverferth ◽

...

Keyword(s):

Binding Site ◽

Gabaa Receptor ◽

Benzodiazepine Binding

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In vitro and in vivo GABAA Receptor Interaction of the Propanidid Metabolite 4-(2-[Diethylamino]-2-Oxoethoxy)-3-Methoxy-Benzeneacetic Acid

Pharmacology ◽

10.1159/000493753 ◽

2018 ◽

Vol 103 (1-2) ◽

pp. 10-16 ◽

Cited By ~ 2

Author(s):

Alessia Cenani ◽

Robert J. Brosnan ◽

Heather K. Knych

Keyword(s):

Gabaa Receptor ◽

Gabaa Receptors ◽

Water Solubility ◽

Plasma Concentrations ◽

Receptor Activation ◽

Receptor Interaction ◽

Dependent Manner ◽

Benzeneacetic Acid

Background: Propanidid is a γ-aminobutyric acid type A (GABAA) receptor agonist general anesthetic and its primary metabolite is 4-(2-[diethylamino]-2-oxoethoxy)-3-methoxy-benzeneacetic acid (DOMBA). Despite having a high water solubility at physiologic pH that might predict low-affinity GABAA receptor interactions, DOMBA is reported to have no effect on GABAA receptor currents, possibly because the DOMBA concentrations studied were simply insufficient to modulate GABAA receptors. Our objectives were to measure the propanidid and DOMBA concentration responses on GABAA receptors and to measure the behavioral responses of DOMBA in mice at concentrations that affect GABAA receptor currents in vitro. Methods: GABAA receptors were expressed in oocytes using clones for the human GABAA α1, β2 and γ2s subunits. The effects of DOMBA (0.2–10 mmol/L) and propanidid (0.001–1 mmol/L) on oocyte GABAA currents were studied using standard 2-electrode voltage clamp techniques. Based on in vitro results, 6 mice received DOMBA 32 mg intraperitoneal and were observed for occurrence of neurologic effects and DOMBA plasma concentration was measured by liquid chromatography tandem mass spectrometry. Results: DOMBA both directly activates GABAA receptors and antagonizes its GABA-mediated opening in a concentration-dependent manner at concentrations between 5–10 and 0.5–10 mmol/L respectively. In vivo, DOMBA produced rapid onset sedation at plasma concentrations that correlate with direct GABAA receptor activation. Conclusion: DOMBA modulation of GABAA receptors is associated with sedation in mice. Metabolites of propanidid analogues currently in development may similarly modulate GABAA, and impaired elimination of these metabolites could produce clinically relevant neurophysiologic effects.

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Tonic Extrasynaptic GABAA Receptor Currents Control Gonadotropin-Releasing Hormone Neuron Excitability in the Mouse

Endocrinology ◽

10.1210/en.2010-1191 ◽

2011 ◽

Vol 152 (4) ◽

pp. 1551-1561 ◽

Cited By ~ 31

Author(s):

Janardhan P. Bhattarai ◽

Seon Ah Park ◽

Jin Bong Park ◽

So Yeong Lee ◽

Allan E. Herbison ◽

...

Keyword(s):

Gabaa Receptor ◽

Gabaa Receptors ◽

Brain Slice ◽

Resting Membrane Potential ◽

Receptor Signaling ◽

Gaba Transporter ◽

Gnrh Neurons ◽

Inward Currents ◽

Synaptic Receptors ◽

Tonic Current

Abstract It is well established that the GABAA receptor plays an important role in regulating the electrical excitability of GnRH neurons. Two different modes of GABAA receptor signaling exist: one mediated by synaptic receptors generating fast (phasic) postsynaptic currents and the other mediated by extrasynaptic receptors generating a persistent (tonic) current. Using GABAA receptor antagonists picrotoxin, bicuculline methiodide, and gabazine, which differentiate between phasic and tonic signaling, we found that ∼50% of GnRH neurons exhibit an approximately 15-pA tonic GABAA receptor current in the acute brain slice preparation. The blockade of either neuronal (NO711) or glial (SNAP-5114) GABA transporter activity within the brain slice revealed the presence of tonic GABA signaling in ∼90% of GnRH neurons. The GABAA receptor δ subunit is only found in extrasynaptic GABAA receptors. Using single-cell RT-PCR, GABAA receptor δ subunit mRNA was identified in GnRH neurons and the δ subunit–specific agonist 4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridin-3-ol was found to activate inward currents in GnRH neurons. Perforated-patch clamp studies showed that 4,5,6,7-tetrahydroisoxazolo [5,4-c] pyridin-3-ol exerted the same depolarizing or hyperpolarizing effects as GABA on juvenile and adult GnRH neurons and that tonic GABAA receptor signaling regulates resting membrane potential. Together, these studies reveal the presence of a tonic GABAA receptor current in GnRH neurons that controls their excitability. The level of tonic current is dependent, in part, on neuronal and glial GABA transporter activity and mediated by extrasynaptic δ subunit–containing GABAA receptors.

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An association study in the Taiwan Biobank elicits the GABAA receptor genes GABRB3, GABRA5, and GABRG3 as candidate loci for sleep duration in the Taiwanese population

BMC Medical Genomics ◽

10.1186/s12920-021-01083-x ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Sheue-Jane Hou ◽

Shih-Jen Tsai ◽

Po-Hsiu Kuo ◽

Wan-Yu Lin ◽

Yu-Li Liu ◽

...

Keyword(s):

Sleep Quality ◽

Association Study ◽

Gabaa Receptor ◽

Sleep Duration ◽

Gabaa Receptors ◽

Aminobutyric Acid ◽

Gamma Aminobutyric Acid ◽

Bonferroni Correction ◽

Taiwanese Population ◽

Sleep Timing

Abstract Background Gamma-aminobutyric acid type A (GABAA) receptors mainly mediate the effects of gamma-aminobutyric acid, which is the primary inhibitory neurotransmitter in the central nervous system. Abundant evidence suggests that GABAA receptors play a key role in sleep-regulating processes. No genetic association study has explored the relationships between GABAA receptor genes and sleep duration, sleep quality, and sleep timing in humans. Methods We determined the association between single-nucleotide polymorphisms (SNPs) in the GABAA receptor genes GABRA1, GABRA2, GABRB3, GABRA5, and GABRG3 and sleep duration, sleep quality, and sleep timing in the Taiwan Biobank with a sample of 10,127 Taiwanese subjects. There were 10,142 subjects in the original study cohort. We excluded 15 subjects with a medication history of sedative-hypnotics. Results Our data revealed an association of the GABRB3-GABRA5-GABRG3 gene cluster with sleep duration, which has not been previously identified: rs79333046 (beta = − 0.07; P = 1.21 × 10–3) in GABRB3, rs189790076 (beta = 0.92; P = 1.04 × 10–3) in GABRA5, and rs147619342 (beta = − 0.72; P = 3.97 × 10–3) in GABRG3. The association between rs189790076 in GABRA5 and sleep duration remained significant after Bonferroni correction. A variant (rs12438141) in GABRB3 was also found to act as a potential expression quantitative trait locus. Additionally, we discovered interactions between variants in the GABRB3-GABRA5-GABRG3 gene cluster and lifestyle factors, such as tea and coffee consumption, smoking, and physical activity, that influenced sleep duration, although some interactions became nonsignificant after Bonferroni correction. We also found interactions among GABRB3, GABRA5, and GABRG3 that affected sleep duration. Furthermore, we identified an association of rs7165524 (beta = − 0.06; P = 2.20 × 10–3) in GABRA5 with sleep quality and an association of rs79465949 (beta = − 0.12; P = 3.95 × 10–3) in GABRB3 with sleep timing, although these associations became nonsignificant after Bonferroni correction. However, we detected no evidence of an association of individual SNPs in GABRA1 and GABRA2. Conclusions Our results indicate that rs189790076 in GABRA5 and gene–gene interactions among GABRB3, GABRA5, and GABRG3 may contribute to sleep duration in the Taiwanese population.

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