1
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Plasil SL, Farris SP, Blednov Y, Mayfield RD, Mangieri RA, Nwokeji UJ, Aziz HC, Lambeth PS, Harris RA, Homanics GE. Mutation of novel ethanol-responsive lncRNA Gm41261 impacts ethanol-related behavioral responses in mice. GENES, BRAIN, AND BEHAVIOR 2024; 23:e12886. [PMID: 38373108 PMCID: PMC10876150 DOI: 10.1111/gbb.12886] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 01/05/2024] [Accepted: 01/26/2024] [Indexed: 02/21/2024]
Abstract
Chronic alcohol exposure results in widespread dysregulation of gene expression that contributes to the pathogenesis of Alcohol Use Disorder (AUD). Long noncoding RNAs are key regulators of the transcriptome that we hypothesize coordinate alcohol-induced transcriptome dysregulation and contribute to AUD. Based on RNA-Sequencing data of human prefrontal cortex, basolateral amygdala and nucleus accumbens of AUD versus non-AUD brain, the human LINC01265 and its predicted murine homolog Gm41261 (i.e., TX2) were selected for functional interrogation. We tested the hypothesis that TX2 contributes to ethanol drinking and behavioral responses to ethanol. CRISPR/Cas9 mutagenesis was used to create a TX2 mutant mouse line in which 306 base-pairs were deleted from the locus. RNA analysis revealed that an abnormal TX2 transcript was produced at an unchanged level in mutant animals. Behaviorally, mutant mice had reduced ethanol, gaboxadol and zolpidem-induced loss of the righting response and reduced tolerance to ethanol in both sexes. In addition, a male-specific reduction in two-bottle choice every-other-day ethanol drinking was observed. Male TX2 mutants exhibited evidence of enhanced GABA release and altered GABAA receptor subunit composition in neurons of the nucleus accumbens shell. In C57BL6/J mice, TX2 within the cortex was cytoplasmic and largely present in Rbfox3+ neurons and IBA1+ microglia, but not in Olig2+ oligodendrocytes or in the majority of GFAP+ astrocytes. These data support the hypothesis that TX2 mutagenesis and dysregulation impacts ethanol drinking behavior and ethanol-induced behavioral responses in mice, likely through alterations in the GABAergic system.
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Affiliation(s)
- S. L. Plasil
- Department of Pharmacology and Chemical BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - S. P. Farris
- Department of Anesthesiology and Perioperative MedicineUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
- Department of Biomedical InformaticsUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
| | - Y. Blednov
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
| | - R. D. Mayfield
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
- Department of NeuroscienceThe University of Texas at AustinAustinTexasUSA
| | - R. A. Mangieri
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
- Division of Pharmacology and Toxicology, College of PharmacyThe University of Texas at AustinAustinTexasUSA
| | - U. J. Nwokeji
- Department of Pharmacology and Chemical BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
| | - H. C. Aziz
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
- Division of Pharmacology and Toxicology, College of PharmacyThe University of Texas at AustinAustinTexasUSA
| | - P. S. Lambeth
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
- Department of NeuroscienceThe University of Texas at AustinAustinTexasUSA
| | - R. A. Harris
- The Waggoner Center for Alcohol and Addiction ResearchThe University of Texas at AustinAustinTexasUSA
| | - G. E. Homanics
- Department of Pharmacology and Chemical BiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
- Department of Anesthesiology and Perioperative MedicineUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
- Department of NeurobiologyUniversity of Pittsburgh School of MedicinePittsburghPennsylvaniaUSA
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2
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Faleschini T, Syafni N, Schulte HL, Garifulina A, Hering S, Espindola LS, Hamburger M. A neolignan from Connarus tuberosus as an allosteric GABA A receptor modulator at the neurosteroid binding site. Biomed Pharmacother 2023; 161:114498. [PMID: 36906973 DOI: 10.1016/j.biopha.2023.114498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Revised: 02/24/2023] [Accepted: 03/07/2023] [Indexed: 03/12/2023] Open
Abstract
In a screening of a small library of extracts from plants of the Amazonian and Cerrado biomes, a hexane extract of Connarus tuberosus roots was found to significantly potentiate the GABA induced fluorescence in a fluorescence (FLIPR) assay in CHO cells stably expressing the α1β2γ2 subtype of human GABAA receptors. With the aid of HPLC-based activity profiling the activity was linked to the neolignan connarin. In CHO cells the activity of connarin was not abolished by increasing concentrations of flumazenil, while the effect of diazepam was increased by increasing concentrations of connarin. The effect of connarin was abolished by pregnenolone sulfate (PREGS) in a concentration-dependent manner, and the effect of allopregnanolone was further increased by increasing concentrations of connarin. In a two-microelectrode voltage clamp assay with Xenopus laevis oocytes transiently expressing GABAA receptors composed of human α1β2γ2S and α1β2 subunits connarin potentiated the GABA-induced currents, with EC50 values of 1.2 ± 0.3 μM (α1β2γ2S) and 1.3 ± 0.4 μM (α1β2), and with a maximum enhancement of currents Emax of 1959 ± 70% (α1β2γ2S) and 185 ± 48% (α1β2). The activation induced by connarin was abolished by increasing concentrations of PREGS.
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Affiliation(s)
- Teresa Faleschini
- Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland
| | - Nova Syafni
- Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland; Faculty of Pharmacy and Sumatran Biota Laboratory, Andalas University, 25163 Padang, West Sumatra, Indonesia
| | - Heidi Luise Schulte
- Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland; Universidade de Brasília, Laboratório de Farmacognosia, Campus Universitário Darcy Ribeiro, 70910-900 Brasília, DF, Brazil
| | - Aleksandra Garifulina
- Division of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, 1090 Vienna, Austria
| | - Steffen Hering
- Universidade de Brasília, Laboratório de Farmacognosia, Campus Universitário Darcy Ribeiro, 70910-900 Brasília, DF, Brazil
| | - Laila Salmen Espindola
- Universidade de Brasília, Laboratório de Farmacognosia, Campus Universitário Darcy Ribeiro, 70910-900 Brasília, DF, Brazil
| | - Matthias Hamburger
- Department of Pharmaceutical Sciences, University of Basel, 4056 Basel, Switzerland.
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3
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Syafni N, Faleschini MT, Garifulina A, Danton O, Gupta MP, Hering S, Hamburger M. Clerodane Diterpenes from Casearia corymbosa as Allosteric GABA A Receptor Modulators. JOURNAL OF NATURAL PRODUCTS 2022; 85:1201-1210. [PMID: 35475609 PMCID: PMC9150179 DOI: 10.1021/acs.jnatprod.1c00840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Indexed: 06/14/2023]
Abstract
An EtOAc extract of Casearia corymbosa leaves led to an allosteric potentiation of the GABA signal in a fluorometric imaging plate reader (FLIPR) assay on Chinese hamster ovary (CHO) cells stably expressing GABAA receptors with an α1β2γ2 subunit composition. The activity was tracked by HPLC-based activity profiling, and four known (2, 3, 4, and 8) and five new clerodane-type diterpenoids (1, 5-7, and 9) were isolated. Compounds 1-8 were obtained from the active time window. The absolute configuration of all compounds was established by ECD. Compounds 3, 7, and 8 exhibited EC50 values of 0.5, 4.6, and 1.4 μM, respectively. To explore possible binding sites at the receptor, the most abundant diterpenoid 8 was tested in combination with diazepam, etazolate, and allopregnanolone. An additive potentiation of the GABA signal was observed with these compounds, while the effect of 8 was not inhibited by flumazenil, a negative allosteric modulator at the benzodiazepine binding site. Finally, the activity was validated in voltage clamp studies on Xenopus laevis oocytes transiently expressing GABAA receptors of the α1β2γ2S and α1β2 subtypes. Compound 8 potentiated GABA-induced currents with both receptor subunit compositions [EC50 (α1β2γ2S) = 43.6 μM; Emax = 809% and EC50 (α1β2) = 57.6 μM; Emax = 534%]. The positive modulation of GABA-induced currents was not inhibited by flumazenil, thereby confirming an allosteric modulation independent of the benzodiazepine binding site.
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Affiliation(s)
- Nova Syafni
- Pharmaceutical
Biology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
- Faculty
of Pharmacy and Sumatran Biota Laboratory, Andalas University, Kampus Limau Manis, Padang, West Sumatra 25175, Indonesia
| | - Maria Teresa Faleschini
- Pharmaceutical
Biology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Aleksandra Garifulina
- Division
of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, Pharmaziezentrum, Althanstrasse 14, 1090 Vienna, Austria
| | - Ombeline Danton
- Pharmaceutical
Biology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
| | - Mahabir P. Gupta
- Center
for Pharmacognostic Research on Panamanian Flora, Faculty of Pharmacy, University of Panama, Panama City 0801, Panama
| | - Steffen Hering
- Division
of Pharmacology and Toxicology, Department of Pharmaceutical Sciences, University of Vienna, Pharmaziezentrum, Althanstrasse 14, 1090 Vienna, Austria
| | - Matthias Hamburger
- Pharmaceutical
Biology, Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, 4056 Basel, Switzerland
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4
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Schmidpeter PAM, Nimigean CM. Correlating ion channel structure and function. Methods Enzymol 2021; 652:3-30. [PMID: 34059287 DOI: 10.1016/bs.mie.2021.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Recent developments in cryogenic electron microscopy (cryo-EM) led to an exponential increase in high-resolution structures of membrane proteins, and in particular ion channels. However, structures alone can only provide limited information about the workings of these proteins. In order to understand ion channel function and regulation in molecular detail, the obtained structural data need to be correlated to functional states of the same protein. Here, we describe several techniques that can be employed to study ion channel structure and function in vitro and under defined, similar conditions. Lipid nanodiscs provide a native-like environment for membrane proteins and have become a valuable tool in membrane protein structural biology and biophysics. Combined with liposome-based flux assays for the kinetic analysis of ion channel activity as well as electrophysiological recordings, researchers now have access to an array of experimental techniques allowing for detailed structure-function correlations using purified components. Two examples are presented where we put emphasis on the lipid environment and time-resolved techniques together with mutations and protein engineering to interpret structural data obtained from single particle cryo-EM on cyclic nucleotide-gated or Ca2+-gated K+ channels. Furthermore, we provide short protocols for all the assays used in our work so that others can adapt these techniques to their experimental needs. Comprehensive structure-function correlations are essential in order to pharmacologically target channelopathies.
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Affiliation(s)
| | - Crina M Nimigean
- Department of Anesthesiology, Weill Cornell Medicine, New York, NY, United States.
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5
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Beato A, Gori A, Boucherle B, Peuchmaur M, Haudecoeur R. β-Carboline as a Privileged Scaffold for Multitarget Strategies in Alzheimer's Disease Therapy. J Med Chem 2021; 64:1392-1422. [PMID: 33528252 DOI: 10.1021/acs.jmedchem.0c01887] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The natural β-carboline alkaloids display similarities with neurotransmitters that can be favorably exploited to design bioactive and bioavailable drugs for Alzheimer's disease (AD) therapy. Several AD targets are currently and intensively being investigated, divided in different hypotheses: mainly the cholinergic, the amyloid β (Aβ), and the Tau hypotheses. To date, only symptomatic treatments are available involving acetylcholinesterase and NMDA inhibitors. On the basis of plethoric single-target structure-activity relationship studies, the β-carboline scaffold was identified as a powerful tool for fostering activity and molecular interactions with a wide range of AD-related targets. This knowledge can undoubtedly be used to design multitarget-directed ligands, a highly relevant strategy preferred in the context of multifactorial pathology with intricate etiology such as AD. In this review, we first individually discuss the AD targets of the β-carbolines, and then we focus on the multitarget strategies dedicated to the deliberate design of new efficient scaffolds.
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Affiliation(s)
| | - Anthonin Gori
- Univ. Grenoble Alpes, CNRS, DPM, 38000 Grenoble, France.,CHANEL Parfums Beauté, F-93500 Pantin, France
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6
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Wang L, Kloc M, Maher E, Erisir A, Maffei A. Presynaptic GABAA Receptors Modulate Thalamocortical Inputs in Layer 4 of Rat V1. Cereb Cortex 2020; 29:921-936. [PMID: 29373653 DOI: 10.1093/cercor/bhx364] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 01/01/2018] [Indexed: 11/14/2022] Open
Abstract
Fast inhibitory GABAergic transmission plays a fundamental role in neural circuits. Current theories of cortical function assume that fast GABAergic inhibition acts via GABAA receptors on postsynaptic neurons, while presynaptic effects of GABA depend on GABAB receptor activation. Manipulations of GABAA receptor activity in vivo produced different effects on cortical function, which were generally ascribed to the mode of action of a drug, more than its site of action. Here we show that in rodent primary visual cortex, α4-containing GABAA receptors can be located on subsets of glutamatergic and GABAergic presynaptic terminals and decrease synaptic transmission. Our data provide a novel mechanistic insight into the effects of changes in cortical inhibition; the ability to modulate inputs onto cortical circuits locally, via presynaptic regulation of release by GABAA receptors.
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Affiliation(s)
- L Wang
- Department of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY, USA
| | - M Kloc
- Department of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY, USA
| | - E Maher
- Department of Psychology, University of Virginia, Charlottesville, VA, USA
| | - A Erisir
- Department of Psychology, University of Virginia, Charlottesville, VA, USA
| | - A Maffei
- Department of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY, USA
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7
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Moniri NH. Reintroduction of quazepam: an update on comparative hypnotic and adverse effects. Int Clin Psychopharmacol 2019; 34:275-285. [PMID: 31274695 DOI: 10.1097/yic.0000000000000277] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Insomnia is a prevalent disorder that affects over one-third of the U.S. population to varying degrees and is highly disruptive towards quality of life. Pharmacological treatments for insomnia include benzodiazepines (BZs) and the non-BZ 'Z-drugs' (zolpidem, zaleplon, eszopiclone, zopiclone), which are amongst the most widely prescribed medications. Yet, these agents can produce adverse effects such as tolerance to the hypnotic effect, rebound insomnia, next-day residual drowsiness, as well as amnesia and complex behaviours such as sleep-walking, sleep-eating and sleep-driving. Quazepam, one of the five BZ approved for treatment of insomnia, was recently relaunched to the U.S. market in 2016 and is distinguished amongst hypnotic BZ by unique pharmacological characteristics including selectivity for sleep-promoting α1-subunit containing γ-aminobutyric acid (GABA-A) receptors and a significantly lower relative receptor binding affinity. These features likely drive the decreased rate of adverse events seen clinically with quazepam, such as tolerance, rebound insomnia and amnesic behaviours, compared with other BZ. Given the recent reintroduction of quazepam as a pharmacotherapeutic option, and the lack of head-to-head comparative trials against newer agents, the purpose of this review is to provide an update on distinguishing features of quazepam with regard to its pharmacology, pharmacokinetics, sleep efficacy and potential adverse effects compared to other agents used for insomnia.
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Affiliation(s)
- Nader H Moniri
- Department of Pharmaceutical Sciences, College of Pharmacy, Mercer University Health Sciences Center, Mercer University, Atlanta, Georgia, USA
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8
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Kwon S, Jung JH, Cho S, Moon KD, Lee J. Dieckol is a natural positive allosteric modulator of GABAA-benzodiazepine receptors and enhances inhibitory synaptic activity in cultured neurons. Nutr Neurosci 2019; 24:835-842. [DOI: 10.1080/1028415x.2019.1681089] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Sangoh Kwon
- S&D Research and Development Institute, Cheongju, Republic of Korea
- Major in Food Biotechnology, School of Food Science & Biotechnology, Kyungpook National University, Daegu, Republic of Korea
| | - Jong Hoon Jung
- Research group of Functional Food Materials, Division of Functional Food, Korea Food Research Institute, Jeollabuk-do, Republic of Korea
| | - Suengmok Cho
- Department of Food Science and Technology, Pukyong National University, Busan, Republic of Korea
| | - Kwang-Deog Moon
- Major in Food Biotechnology, School of Food Science & Biotechnology, Kyungpook National University, Daegu, Republic of Korea
| | - Jaekwang Lee
- Research group of Functional Food Materials, Division of Functional Food, Korea Food Research Institute, Jeollabuk-do, Republic of Korea
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9
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JoonWoo Han, Young-Jin Ko, Byung-Joo Park, Seonji Kim. Signal Detection of Adverse Drug Reaction of Zolpidem Using the Korea Adverse Event Reporting System Database. ACTA ACUST UNITED AC 2018. [DOI: 10.34161/johta.2018.6.1.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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10
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Chandler CM, Overton JS, Rüedi-Bettschen D, Platt DM. GABA A Receptor Subtype Mechanisms and the Abuse-Related Effects of Ethanol: Genetic and Pharmacological Evidence. Handb Exp Pharmacol 2018; 248:3-27. [PMID: 29204713 DOI: 10.1007/164_2017_80] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ethanol's reinforcing and subjective effects, as well as its ability to induce relapse, are powerful factors contributing to its widespread use and abuse. A significant mediator of these behavioral effects is the GABAA receptor system. GABAA receptors are the target for γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the CNS. Structurally, they are pentameric, transmembrane chloride ion channels comprised of subunits from at least eight different families of distinct proteins. The contribution of different GABAA subunits to ethanol's diverse abuse-related effects is not clear and remains an area of research focus. This chapter details the clinical and preclinical findings supporting roles for different α, β, γ, and δ subunit-containing GABAA receptors in ethanol's reinforcing, subjective/discriminative stimulus, and relapse-inducing effects. The reinforcing properties of ethanol have been studied the most systematically, and convergent preclinical evidence suggests a key role for the α5 subunit in those effects. Regarding ethanol's subjective/discriminative stimulus effects, clinical and genetic findings support a primary role for the α2 subunit, whereas preclinical evidence implicates the α5 subunit. At present, too few studies investigating ethanol relapse exist to make any solid conclusions regarding the role of specific GABAA subunits in this abuse-related effect.
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Affiliation(s)
- Cassie M Chandler
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA
| | - John S Overton
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Daniela Rüedi-Bettschen
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Donna M Platt
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA.
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA.
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11
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Moradi-Afrapoli F, Ebrahimi SN, Smiesko M, Hamburger M. HPLC-Based Activity Profiling for GABA A Receptor Modulators in Extracts: Validation of an Approach Utilizing a Larval Zebrafish Locomotor Assay. JOURNAL OF NATURAL PRODUCTS 2017; 80:1548-1557. [PMID: 28485933 DOI: 10.1021/acs.jnatprod.7b00081] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Gamma-aminobutyric acid type A (GABAA) receptors are major inhibitory neurotransmitter receptors in the central nervous system and a target for numerous clinically important drugs used to treat anxiety, insomnia, and epilepsy. A series of allosteric GABAA receptor agonists was identified previously with the aid of HPLC-based activity profiling, whereby activity was tracked with an electrophysiological assay in Xenopus laevis oocytes. To accelerate the discovery process, an approach has been established for HPLC-based profiling using a larval zebrafish (Danio rerio) seizure model induced by pentylenetetrazol (PTZ), a pro-convulsant GABAA receptor antagonist. The assay was validated with the aid of representative GABAergic plant compounds and extracts. Various parameters that are relevant for the quality of results obtained, including PTZ concentration, the number of larvae, the incubation time, and the data analysis protocol, were optimized. The assay was then translated into an HPLC profiling protocol, and active compounds were tracked in extracts of Valeriana officinalis and Magnolia officinalis. For selected compounds the effects in the zebrafish larvae model were compared with data from in silico blood-brain barrier (BBB) permeability predictions, to validate the use for discovery of BBB-permeable natural products.
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Affiliation(s)
| | - Samad Nejad Ebrahimi
- Department of Phytochemistry, Medicinal Plants and Drugs Research Institute, Shahid Beheshti University , G. C., Evin, Tehran, Iran
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12
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Berro LF, Andersen ML, Tufik S, Howell LL. GABA A receptor positive allosteric modulators modify the abuse-related behavioral and neurochemical effects of methamphetamine in rhesus monkeys. Neuropharmacology 2017; 123:299-309. [PMID: 28495376 DOI: 10.1016/j.neuropharm.2017.05.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2016] [Revised: 05/01/2017] [Accepted: 05/07/2017] [Indexed: 12/21/2022]
Abstract
GABAA receptor positive allosteric modulators (GABAA receptor modulators) are commonly used for the treatment of insomnia. Nevertheless, the effects of these compounds on psychostimulant-induced sleep impairment are poorly understood. Because GABAA receptor modulators have been shown to decrease the abuse-related effects of psychostimulants, the aim of the present study was to evaluate the effects of temazepam (0.3, 1.0 or 3.0 mg/kg) and eszopiclone (0.3, 1.0 or 3.0 mg/kg), two GABAA receptor modulators, on the behavioral neuropharmacology of methamphetamine in adult rhesus macaques (n = 5). Sleep-like measures and general daytime activity were evaluated with Actiwatch monitors. Methamphetamine self-administration (0.03 mg/kg/inf) was evaluated during morning sessions. Methamphetamine-induced dopamine overflow was assessed through in vivo microdialysis targeting the nucleus accumbens. Nighttime treatment with either temazepam or eszopiclone was ineffective in improving sleep-like measures disrupted by methamphetamine self-administration. Acute pretreatment with a low dose of temazepam before self-administration sessions increased methamphetamine self-administration without affecting normal daytime home-cage activity. At a high dose, acute temazepam pretreatment decreased methamphetamine self-administration and attenuated methamphetamine-induced increases in dopamine in the nucleus accumbens, without decreasing general daytime activity. Acute eszopiclone treatment exerted no effects on methamphetamine intake or drug-induced increases in dopamine. Our study suggests that treatments based on GABAA receptor modulators are not effective for the treatment of sleep disruption in the context of psychostimulant use. In addition, distinct GABAA receptor modulators differentially modulated the abuse-related effects of methamphetamine, with acute treatment with the high efficacy GABAA receptor modulator temazepam decreasing the behavioral and neurochemical effects of methamphetamine.
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Affiliation(s)
- Laís F Berro
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road N.E., Atlanta, GA 30329, USA; Department of Psychobiology, Universidade Federal de São Paulo, R. Napoleão de Barros, 925, 04021002 São Paulo, SP, Brazil
| | - Monica L Andersen
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road N.E., Atlanta, GA 30329, USA; Department of Psychobiology, Universidade Federal de São Paulo, R. Napoleão de Barros, 925, 04021002 São Paulo, SP, Brazil
| | - Sergio Tufik
- Department of Psychobiology, Universidade Federal de São Paulo, R. Napoleão de Barros, 925, 04021002 São Paulo, SP, Brazil
| | - Leonard L Howell
- Yerkes National Primate Research Center, Emory University, 954 Gatewood Road N.E., Atlanta, GA 30329, USA; Department of Psychiatry and Behavioral Sciences, School of Medicine, Emory University, 954 Gatewood Road N.E., Atlanta, GA 30329, USA.
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13
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Involvement of ATP-sensitive potassium channels and the opioid system in the anticonvulsive effect of zolpidem in mice. Epilepsy Behav 2016; 62:291-6. [PMID: 27521722 DOI: 10.1016/j.yebeh.2016.07.014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 07/05/2016] [Accepted: 07/06/2016] [Indexed: 01/30/2023]
Abstract
Zolpidem is a hypnotic medication that mainly exerts its function through activating γ-aminobutyric acid (GABA)A receptors. There is some evidence that zolpidem may have anticonvulsive effects. However, the mechanisms underlying this effect have not been elucidated yet. In the present study, we used the pentylentetrazole (PTZ)-induced generalized seizure model in mice to investigate whether zolpidem can affect seizure threshold. We also further evaluated the roles of ATP-sensitive potassium (KATP) channels as well as μ-opioid receptors in the effects of zolpidem on seizure threshold. Our data showed that zolpidem in a dose-dependent manner increased the PTZ-induced seizure threshold. The noneffective (i.e., did not significantly alter the PTZ-induced seizure threshold by itself) doses of KATP channel blocker (glibenclamide) and nonselective opioid receptor antagonist (naloxone) were able to inhibit the anticonvulsive effect of zolpidem. Additionally, noneffective doses of either KATP channel opener (cromakalim) or nonselective μ-opioid receptor agonist (morphine) in combination with a noneffective dose of zolpidem exerted a significant anticonvulsive effect on PTZ-induced seizures in mice. A combination of noneffective doses of naloxone and glibenclamide, which separately did not affect zolpidem effect on seizure threshold, inhibited the anticonvulsive effects of zolpidem. These results suggest a role for KATP channels and the opioid system, alone or in combination, in the anticonvulsive effects of zolpidem.
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14
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Kozono A, Isami K, Shiota K, Tsumagari K, Nagano M, Inoue D, Adachi R, Hiraki Y, Nakagawa Y, Kamimura H, Yamamichi K. Relationship of Prescribed Drugs with the Risk of Fall in Inpatients. YAKUGAKU ZASSHI 2016; 136:769-76. [DOI: 10.1248/yakushi.15-00245] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Aki Kozono
- Department of Pharmacy, National Hospital Organization Kumamoto Saishunso Hospital
| | - Keisuke Isami
- Department of Pharmacy, National Hospital Organization Kumamoto Saishunso Hospital
| | - Kimiko Shiota
- Department of Pharmacy, National Hospital Organization Kumamoto Saishunso Hospital
| | - Kyouichi Tsumagari
- Department of Pharmacy, National Hospital Organization Kumamoto Saishunso Hospital
| | - Masahisa Nagano
- Department of Pharmacy, National Hospital Organization Kumamoto Medical Center
| | - Daisuke Inoue
- Department of Pharmacy, National Hospital Organization Kumamoto Medical Center
| | - Rui Adachi
- Department of Pharmacy, National Hospital Organization Beppu Medical Center
| | - Yoichi Hiraki
- Department of Pharmacy, National Hospital Organization Beppu Medical Center
| | - Yoshihiro Nakagawa
- Department of Pharmacy, National Hospital Organization Kumamoto Medical Center
| | | | - Ken Yamamichi
- Department of Pharmacy, National Hospital Organization Kumamoto Saishunso Hospital
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15
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Tracy ME, Banks ML, Shelton KL. Negative allosteric modulation of GABAA receptors inhibits facilitation of brain stimulation reward by drugs of abuse in C57BL6/J mice. Psychopharmacology (Berl) 2016; 233:715-25. [PMID: 26612620 PMCID: PMC4825185 DOI: 10.1007/s00213-015-4155-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 11/04/2015] [Indexed: 10/22/2022]
Abstract
RATIONALE There is an emerging body of evidence that implicates a crucial role of γ-aminobutyric acid subtype A (GABAA) receptors in modulating the rewarding effects of a number of abused drugs. Modulation of GABAA receptors may therefore represent a novel drug-class independent mechanism for the development of abuse treatment pharmacotherapeutics. OBJECTIVES We tested the hypothesis that the GABAA receptor benzodiazepine-site (BDZ) negative modulator Ro15-4513 would reduce the reward-related effects of three pharmacologically dissimilar drugs; toluene vapor, d-methamphetamine, and diazepam using intracranial self-stimulation (ICSS) in mice. We also examined whether Ro15-4513 attenuated dopamine release produced by d-methamphetamine in an in vivo microdialysis procedure. RESULTS Ro15-4513 abolished ICSS reward facilitation produced by all three abused drugs at Ro15-4513 doses which had no effect on ICSS when administered alone. In contrast, the BDZ antagonist flumazenil only attenuated the ICSS-facilitating effects of diazepam. Administration of the same dose of Ro15-4513 which abolished drug-facilitated ICSS produced a 58 % decrease in d-methamphetamine-stimulated dopamine in the nucleus accumbens of mice relative to d-methamphetamine alone. CONCLUSIONS These results demonstrate that negative modulation of GABAA receptors can produce profound reductions in reward-related effects of a diverse group of drugs that activate the mesolimbic reward pathway through different mechanisms. These data suggest that pharmacological modulation of GABAA receptors may represent a viable pathway for the development of drug abuse pharmacotherapies.
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Affiliation(s)
- Matthew E. Tracy
- Department of Pharmacology and Toxicology, Virginia Commonwealth University
| | - Matthew L. Banks
- Dept. of Pharmacology and Toxicology, Virginia Commonwealth University
| | - Keith L. Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University
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16
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Gravielle MC. Activation-induced regulation of GABAA receptors: Is there a link with the molecular basis of benzodiazepine tolerance? Pharmacol Res 2015; 109:92-100. [PMID: 26733466 DOI: 10.1016/j.phrs.2015.12.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 12/21/2015] [Accepted: 12/22/2015] [Indexed: 12/01/2022]
Abstract
Benzodiazepines have been used clinically for more than 50 years to treat disorders such as insomnia, anxiety, and epilepsy, as well as to aid muscle relaxation and anesthesia. The therapeutic index for benzodiazepines if very high and the toxicity is low. However, their usefulness is limited by the development of either or both tolerance to most of their pharmacological actions and dependence. Tolerance develops at different rates depending on the pharmacological action, suggesting the existence of distinct mechanisms for each behavioral parameter. Alternatively, multiple mechanisms could coexist depending on the subtype of GABAA receptor expressed and the brain region involved. Because most of the pharmacological actions of benzodiazepines are mediated through GABAA receptor binding, adaptive alterations in the number, structure, and/or functions of these receptors may play an important role in the development of tolerance. This review is focused on the regulation of GABAA receptors induced by long-term benzodiazepine exposure and its relationship with the development of tolerance. Understanding the mechanisms behind benzodiazepine tolerance is critical for designing drugs that could maintain their efficacy during long-term treatments.
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Affiliation(s)
- María Clara Gravielle
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
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17
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Tolerance to the sedative and anxiolytic effects of diazepam is associated with different alterations of GABAA receptors in rat cerebral cortex. Neuroscience 2015; 310:152-62. [DOI: 10.1016/j.neuroscience.2015.09.038] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 09/11/2015] [Accepted: 09/12/2015] [Indexed: 11/18/2022]
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18
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Farb DH, Ratner MH. Targeting the modulation of neural circuitry for the treatment of anxiety disorders. Pharmacol Rev 2015; 66:1002-32. [PMID: 25237115 DOI: 10.1124/pr.114.009126] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anxiety disorders are a major public health concern. Here, we examine the familiar area of anxiolysis in the context of a systems-level understanding that will hopefully lead to revealing an underlying pharmacological connectome. The introduction of benzodiazepines nearly half a century ago markedly improved the treatment of anxiety disorders. These agents reduce anxiety rapidly by allosterically enhancing the postsynaptic actions of GABA at inhibitory type A GABA receptors but side effects limit their use in chronic anxiety disorders. Selective serotonin reuptake inhibitors and serotonin/norepinephrine reuptake inhibitors have emerged as an effective first-line alternative treatment of such anxiety disorders. However, many individuals are not responsive and side effects can be limiting. Research into a relatively new class of agents known as neurosteroids has revealed novel modulatory sites and mechanisms of action that are providing insights into the pathophysiology of certain anxiety disorders, potentially bridging the gap between the GABAergic and serotonergic circuits underlying anxiety. However, translating the pharmacological activity of compounds targeted to specific receptor subtypes in rodent models of anxiety to effective therapeutics in human anxiety has not been entirely successful. Since modulating any one of several broad classes of receptor targets can produce anxiolysis, we posit that a systems-level discovery platform combined with an individualized medicine approach based on noninvasive brain imaging would substantially advance the development of more effective therapeutics.
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Affiliation(s)
- David H Farb
- Laboratory of Molecular Neurobiology, Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts
| | - Marcia H Ratner
- Laboratory of Molecular Neurobiology, Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, Massachusetts
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19
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Model-based meta-analysis of the effects of non-selective and α1-selective GABAA receptor agonists in healthy volunteers. Eur J Clin Pharmacol 2015; 71:1209-21. [DOI: 10.1007/s00228-015-1918-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Accepted: 07/28/2015] [Indexed: 10/23/2022]
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20
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Abstract
Because of proven efficacy, reduced side effects, and less concern about addiction, non-benzodiazepine receptor agonists (non-BzRA) have become the most commonly prescribed hypnotic agents to treat onset and maintenance insomnia. First-line treatment is cognitive-behavioral therapy. When pharmacologic treatment is indicated, non-BzRA are first-line agents for the short-term and long-term management of transient and chronic insomnia related to adjustment, psychophysiologic, primary, and secondary causation. In this article, the benefits and risks of non-BzRA are reviewed, and the selection of a hypnotic agent is defined, based on efficacy, pharmacologic profile, and adverse events.
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Affiliation(s)
- Philip M Becker
- Department of Psychiatry, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, USA; Sleep Medicine Associates of Texas, 5477 Glen Lakes Drive, Suite 100, Dallas, TX 75231, USA.
| | - Manya Somiah
- Sleep Medicine Associates of Texas, 5477 Glen Lakes Drive, Suite 100, Dallas, TX 75231, USA
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21
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Chetty M, Rose RH, Abduljalil K, Patel N, Lu G, Cain T, Jamei M, Rostami-Hodjegan A. Applications of linking PBPK and PD models to predict the impact of genotypic variability, formulation differences, differences in target binding capacity and target site drug concentrations on drug responses and variability. Front Pharmacol 2014; 5:258. [PMID: 25505415 PMCID: PMC4244809 DOI: 10.3389/fphar.2014.00258] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023] Open
Abstract
This study aimed to demonstrate the added value of integrating prior in vitro data and knowledge-rich physiologically based pharmacokinetic (PBPK) models with pharmacodynamics (PDs) models. Four distinct applications that were developed and tested are presented here. PBPK models were developed for metoprolol using different CYP2D6 genotypes based on in vitro data. Application of the models for prediction of phenotypic differences in the pharmacokinetics (PKs) and PD compared favorably with clinical data, demonstrating that these differences can be predicted prior to the availability of such data from clinical trials. In the second case, PK and PD data for an immediate release formulation of nifedipine together with in vitro dissolution data for a controlled release (CR) formulation were used to predict the PK and PD of the CR. This approach can be useful to pharmaceutical scientists during formulation development. The operational model of agonism was used in the third application to describe the hypnotic effects of triazolam, and this was successfully extrapolated to zolpidem by changing only the drug related parameters from in vitro experiments. This PBPK modeling approach can be useful to developmental scientists who which to compare several drug candidates in the same therapeutic class. Finally, differences in QTc prolongation due to quinidine in Caucasian and Korean females were successfully predicted by the model using free heart concentrations as an input to the PD models. This PBPK linked PD model was used to demonstrate a higher sensitivity to free heart concentrations of quinidine in Caucasian females, thereby providing a mechanistic understanding of a clinical observation. In general, permutations of certain conditions which potentially change PK and hence PD may not be amenable to the conduct of clinical studies but linking PBPK with PD provides an alternative method of investigating the potential impact of PK changes on PD.
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Affiliation(s)
| | - Rachel H Rose
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Khaled Abduljalil
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Nikunjkumar Patel
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Gaohua Lu
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Theresa Cain
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Masoud Jamei
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK
| | - Amin Rostami-Hodjegan
- Simcyp Limited (a Certara Company), Blades Enterprise Centre Sheffield, UK ; Manchester Pharmacy School, University of Manchester Manchester, UK
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22
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V’yunova TV, Andreeva LA, Shevchenko KV, Shevchenko VP, Myasoedov NF. Peptide regulation of specific ligand-receptor interactions of GABA with the plasma membranes of nerve cells. NEUROCHEM J+ 2014. [DOI: 10.1134/s1819712414040114] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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23
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Priya S S, Dl B, T S. Zolpidem induced hyponatremia: a case report. J Clin Diagn Res 2014; 8:HD03-4. [PMID: 25386461 DOI: 10.7860/jcdr/2014/10031.4901] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Accepted: 07/30/2014] [Indexed: 11/24/2022]
Abstract
Zolpidem is a non-benzodiazepine hypnotic that acts by binding to (GABAA) receptor. This is a case report of a patient with chronic insomnia for which he had initially been receiving benzodiazepine hypnotic alprazolam and for the past three years, he had switched himself to non-benzodiazepine hypnotic, zolpidem and had progressively increased the dose to 20 mg. The patient presented with history of drowsiness, nausea and vomiting of short duration. Investigations revealed that the patient had hyponatremia. Decreased serum sodium, elevated urine sodium with normal urine osmolarity was detected. Therefore, we report this as a case of drug induced syndrome of inappropriate antidiuretic hormone (SIADH) as other likely causes were ruled out by appropriate investigations. The causality assessment was done according to the WHO scale and found to be "Probable".
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Affiliation(s)
- Shanmuga Priya S
- Assistant Professor, Department of Pharmacology, PSG Institute of Medical Sciences & Research , Off Avinashi Road, Peelamedu, Coimbatore, Tamilnadu, India
| | - Britto Dl
- Clinical Pharmacist, Department of Pharmacy Practice, PSG Institute of Medical Sciences & Research , Off Avinashi Road, Peelamedu, Coimbatore, Tamilnadu, India
| | - Saravanan T
- Professor, Department of Medicine, PSG Institute of Medical Sciences & Research , Off Avinashi Road, Peelamedu, Coimbatore, Tamilnadu, India
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24
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Varagic Z, Ramerstorfer J, Huang S, Rallapalli S, Sarto-Jackson I, Cook J, Sieghart W, Ernst M. Subtype selectivity of α+β- site ligands of GABAA receptors: identification of the first highly specific positive modulators at α6β2/3γ2 receptors. Br J Pharmacol 2014; 169:384-99. [PMID: 23472935 DOI: 10.1111/bph.12153] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 12/21/2012] [Accepted: 01/31/2013] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE GABAA receptors are the major inhibitory neurotransmitter receptors in the mammalian brain and the target of many clinically important drugs interacting with different binding sites. Recently, we demonstrated that CGS 9895 (2-(4-methoxyphenyl)-2H-pyrazolo[4,3-c]quinolin-3(5H)-one) elicits a strong and subtype-dependent enhancement of GABA-induced currents via a novel drug-binding site at extracellular αx+βy- (x = 1-6, y = 1-3) interfaces. Here, we investigated 16 structural analogues of CGS 9895 for their ability to modulate GABA-induced currents of various GABAA receptor subtypes. EXPERIMENTAL APPROACH Recombinant GABAA receptor subtypes were expressed in Xenopus laevis oocytes and investigated by the two-electrode voltage clamp method. KEY RESULTS Most of the compounds investigated were able to modulate GABA-induced currents of αβ and αβγ receptors to a comparable extent, suggesting that the effect of these drugs is not dependent on the benzodiazepine site of GABAA receptors. Steric hindrance experiments demonstrated that these compounds exert their action predominantly via the αx+βy- (x = 1-6, y = 1-3) interfaces. Whereas some compounds are unselectively modulating a broad range of receptor subtypes, other compounds feature remarkable functional selectivity for the α6β3γ2 receptor, or behave as null modulators at some receptor subtypes investigated. CONCLUSION AND IMPLICATIONS Pyrazoloquinolinones and pyrazolopyridinones represent the first prototypes of drugs exerting benzodiazepine-like modulatory effects via the α+β- interface of GABAA receptors. The discovery of modulators with functional subtype selectivity at this class of binding sites provides a highly useful tool for the investigation of α6β2/3γ2 receptor function, and may lead to novel therapeutic principles.
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Affiliation(s)
- Zdravko Varagic
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Vienna, Austria
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25
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Varagic Z, Wimmer L, Schnürch M, Mihovilovic MD, Huang S, Rallapalli S, Cook JM, Mirheydari P, Ecker GF, Sieghart W, Ernst M. Identification of novel positive allosteric modulators and null modulators at the GABAA receptor α+β- interface. Br J Pharmacol 2014; 169:371-83. [PMID: 23472852 DOI: 10.1111/bph.12151] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 12/21/2012] [Accepted: 01/31/2013] [Indexed: 02/03/2023] Open
Abstract
BACKGROUND AND PURPOSE GABAA receptors are the major inhibitory neurotransmitter receptors in the mammalian brain and the target of many clinically important drugs interacting with different binding sites. Recently, we demonstrated that CGS 9895 (2-(4-methoxyphenyl)-2H-pyrazolo[4,3-c]quinolin-3(5H)-one) acts as a null modulator (antagonist) at the high affinity benzodiazepine binding site, but in addition elicits a strong enhancement of GABA-induced currents via a novel drug binding site at the extracellular α+β- interface. Here, we investigated 32 structural analogues of CGS 9895 for their ability to mediate their effects via the α1+β3- interface of GABAA receptors. EXPERIMENTAL APPROACH GABAA receptors were expressed in Xenopus laevis oocytes and investigated by the two-electrode voltage clamp method. KEY RESULTS We not only identified compounds with higher efficacy/potency than CGS 9895 for stimulating GABA-induced currents via the α1+β3-binding site, but also discovered compounds acting as null modulators at this site. Most of the compounds also acted as null modulators via the benzodiazepine binding site of GABAA receptors. But some of the positive allosteric modulators or null modulators exclusively exerted their action via the α+β- binding site. CONCLUSION AND IMPLICATIONS Pyrazoloquinolinones and pyrazolopyridinones represent the first prototype of drug candidates mediating benzodiazepine like modulatory effects via the α+β-interface of GABAA receptors. The discovery of null modulators acting as inhibitors of the plus modulators provides a highly useful tool for the discovery of additional classes of compounds that can modulate GABAA receptors via this site, which may lead to novel therapeutic principles.
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Affiliation(s)
- Zdravko Varagic
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, Vienna, Austria
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26
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Howard P, Twycross R, Shuster J, Mihalyo M, Wilcock A. Benzodiazepines. J Pain Symptom Manage 2014; 47:955-64. [PMID: 24681184 DOI: 10.1016/j.jpainsymman.2014.03.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 02/06/2014] [Indexed: 12/15/2022]
Affiliation(s)
- Paul Howard
- Earl Mountbatten Hospice, Isle of Wight, United Kingdom
| | | | | | - Mary Mihalyo
- Mylan School of Pharmacy, Duquesne University, Pittsburgh, Pennsylvania, USA
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27
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The behavioral pharmacology of zolpidem: evidence for the functional significance of α1-containing GABA(A) receptors. Psychopharmacology (Berl) 2014; 231:1865-96. [PMID: 24563183 DOI: 10.1007/s00213-014-3457-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 01/11/2014] [Indexed: 10/25/2022]
Abstract
RATIONALE Zolpidem is a positive allosteric modulator of γ-aminobutyric acid (GABA) with preferential binding affinity and efficacy for α1-subunit containing GABA(A) receptors (α1-GABA(A)Rs). Over the last three decades, a variety of animal models and experimental procedures have been used in an attempt to relate the behavioral profile of zolpidem and classic benzodiazepines (BZs) to their interaction with α1-GABA(A)Rs. OBJECTIVES This paper reviews the results of rodent and non-human primate studies that have evaluated the effects of zolpidem on motor behaviors, anxiety, memory, food and fluid intake, and electroencephalogram (EEG) sleep patterns. Also included are studies that examined zolpidem's discriminative, reinforcing, and anticonvulsant effects as well as behavioral signs of tolerance and withdrawal. RESULTS The literature reviewed indicates that α1-GABA(A)Rs play a principle role in mediating the hypothermic, ataxic-like, locomotor- and memory-impairing effects of zolpidem and BZs. Evidence also suggests that α1-GABA(A)Rs play partial roles in the hypnotic, EEG sleep, anticonvulsant effects, and anxiolytic-like of zolpidem and diazepam. These studies also indicate that α1-GABA(A)Rs play a more prominent role in mediating the discriminative stimulus, reinforcing, hyperphagic, and withdrawal effects of zolpidem and BZs in primates than in rodents. CONCLUSIONS The psychopharmacological data from both rodents and non-human primates suggest that zolpidem has a unique pharmacological profile when compared with classic BZs. The literature reviewed here provides an important framework for studying the role of different GABA(A)R subtypes in the behavioral effects of BZ-type drugs and helps guide the development of new pharmaceutical agents for disorders currently treated with BZ-type drugs.
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28
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Gutiérrez ML, Ferreri MC, Farb DH, Gravielle MC. GABA-induced uncoupling of GABA/benzodiazepine site interactions is associated with increased phosphorylation of the GABAA receptor. J Neurosci Res 2014; 92:1054-61. [PMID: 24723313 DOI: 10.1002/jnr.23387] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 02/14/2014] [Accepted: 02/26/2014] [Indexed: 11/08/2022]
Abstract
The use-dependent regulation of the GABAA receptor occurs under physiological, pathological, and pharmacological conditions. Tolerance induced by prolonged administration of benzodiazepines is associated with changes in GABAA receptor function. Chronic exposure of neurons to GABA for 48 hr induces a downregulation of the GABAA receptor number and an uncoupling of the GABA/benzodiazepine site interactions. A single brief exposure ((t1/2) = 3 min) of rat neocortical neurons to the neurotransmitter initiates a process that results in uncoupling hours later (t(1/2) = 12 hr) without alterations in the number of GABAA receptors and provides a paradigm to study the uncoupling mechanism selectively. Here we report that uncoupling induced by a brief GABAA receptor activation is blocked by the coincubation with inhibitors of protein kinases A and C, indicating that the uncoupling is mediated by the activation of a phosphorylation cascade. GABA-induced uncoupling is accompanied by subunit-selective changes in the GABAA receptor mRNA levels. However, the GABA-induced downregulation of the α3 subunit mRNA level is not altered by the kinase inhibitors, suggesting that the uncoupling is the result of a posttranscriptional regulatory process. GABA exposure also produces an increase in the serine phosphorylation on the GABAA receptor γ2 subunit. Taken together, our results suggest that the GABA-induced uncoupling is mediated by a posttranscriptional mechanism involving an increase in the phosphorylation of GABAA receptors. The uncoupling of the GABAA receptor may represent a compensatory mechanism to control GABAergic neurotransmission under conditions in which receptors are persistently activated.
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Affiliation(s)
- María L Gutiérrez
- Instituto de Investigaciones Farmacológicas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad de Buenos Aires, Buenos Aires, Argentina
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29
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Qi J, Wang Y, Liu Y, Zhang F, Guan B, Zhang H. Development and validation of HTS assay for screening the calcium-activated chloride channel modulators in TMEM16A stably expressed CHO cells. Anal Bioanal Chem 2014; 406:1713-21. [PMID: 24448969 DOI: 10.1007/s00216-013-7550-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Revised: 11/30/2013] [Accepted: 12/02/2013] [Indexed: 12/18/2022]
Abstract
Calcium-activated chloride channels (CaCCs), for example TMEM16A, are widely expressed in a variety of tissues and are involved in many important physiological functions. We developed and validated an atomic absorption spectroscopy (AAS)-based detection system for high-throughput screening (HTS) of CaCC modulators. With this assay, Cl(-) flux from CHO cells stably transfected with TMEM16A is assayed indirectly, by measuring excess silver ions (Ag(+)) in the supernatant of AgCl precipitates. The screening process involved four steps: (1) TMEM16A CHO cells were incubated in high-K(+) and high-Cl(-) buffer with test compounds, and with ionomycin as Ca(2+) ionophore, for 12 min; (2) cells were washed with a low-K(+), Cl(-)-free and Ca(2+)-free buffer; (3) CaCC/TMEM16A were activated in high-K(+), Cl(-)-free buffer with ionomycin (10 μmol L(-1)) for 12 min; and (4) excess Ag(+) concentration was measured using an ion channel reader (ICR, an AAS system). The assay can be used to screen CaCC activators and inhibitors at the same time. With this assay, positive control drugs, including NPPB, CaCCinh-A01, flufenamic acid (Flu) and Eact, all had good concentration-dependent effects on CaCC/TMEM16A. NPPB and CaCCinh-A01 inhibited the CaCC/TMEM16A currents completely at 300 μmol L(-1), with IC50 values of 39.35 ± 4.72 μmol L(-1) and 6.35 ± 0.27 μmol L(-1), respectively; and Eact, activated CaCC/TMEM16A, with an EC50 value of 3.92 ± 0.87 μmol L(-1).
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Affiliation(s)
- Jinlong Qi
- The Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang, 050017, China
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30
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Gutiérrez M, Ferreri M, Gravielle M. GABA-induced uncoupling of GABA/benzodiazepine site interactions is mediated by increased GABAA receptor internalization and associated with a change in subunit composition. Neuroscience 2014; 257:119-29. [DOI: 10.1016/j.neuroscience.2013.10.077] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2013] [Revised: 10/29/2013] [Accepted: 10/30/2013] [Indexed: 01/11/2023]
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Inoue M, Harada K, Nakamura J, Matsuoka H. Regulation of α3-containing GABAA receptors in guinea-pig adrenal medullary cells by adrenal steroids. Neuroscience 2013; 253:245-55. [DOI: 10.1016/j.neuroscience.2013.08.046] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2013] [Revised: 08/23/2013] [Accepted: 08/24/2013] [Indexed: 12/14/2022]
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32
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Carver CM, Reddy DS. Neurosteroid interactions with synaptic and extrasynaptic GABA(A) receptors: regulation of subunit plasticity, phasic and tonic inhibition, and neuronal network excitability. Psychopharmacology (Berl) 2013; 230:151-88. [PMID: 24071826 PMCID: PMC3832254 DOI: 10.1007/s00213-013-3276-5] [Citation(s) in RCA: 171] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 08/29/2013] [Indexed: 12/25/2022]
Abstract
RATIONALE Neurosteroids are steroids synthesized within the brain with rapid effects on neuronal excitability. Allopregnanolone, allotetrahydrodeoxycorticosterone, and androstanediol are three widely explored prototype endogenous neurosteroids. They have very different targets and functions compared to conventional steroid hormones. Neuronal γ-aminobutyric acid (GABA) type A (GABA(A)) receptors are one of the prime molecular targets of neurosteroids. OBJECTIVE This review provides a critical appraisal of recent advances in the pharmacology of endogenous neurosteroids that interact with GABA(A) receptors in the brain. Neurosteroids possess distinct, characteristic effects on the membrane potential and current conductance of the neuron, mainly via potentiation of GABA(A) receptors at low concentrations and direct activation of receptor chloride channel at higher concentrations. The GABA(A) receptor mediates two types of inhibition, now characterized as synaptic (phasic) and extrasynaptic (tonic) inhibition. Synaptic release of GABA results in the activation of low-affinity γ2-containing synaptic receptors, while high-affinity δ-containing extrasynaptic receptors are persistently activated by the ambient GABA present in the extracellular fluid. Neurosteroids are potent positive allosteric modulators of synaptic and extrasynaptic GABA(A) receptors and therefore enhance both phasic and tonic inhibition. Tonic inhibition is specifically more sensitive to neurosteroids. The resulting tonic conductance generates a form of shunting inhibition that controls neuronal network excitability, seizure susceptibility, and behavior. CONCLUSION The growing understanding of the mechanisms of neurosteroid regulation of the structure and function of the synaptic and extrasynaptic GABA(A) receptors provides many opportunities to create improved therapies for sleep, anxiety, stress, epilepsy, and other neuropsychiatric conditions.
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Affiliation(s)
- Chase Matthew Carver
- Department of Neuroscience and Experimental Therapeutics, College of Medicine, Texas A&M University Health Science Center, 2008 Medical Research and Education Building, 8447 State Highway 47, Bryan, TX, 77807-3260, USA
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Greenfield LJ. Molecular mechanisms of antiseizure drug activity at GABAA receptors. Seizure 2013; 22:589-600. [PMID: 23683707 PMCID: PMC3766376 DOI: 10.1016/j.seizure.2013.04.015] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2013] [Revised: 04/16/2013] [Accepted: 04/17/2013] [Indexed: 02/09/2023] Open
Abstract
The GABAA receptor (GABAAR) is a major target of antiseizure drugs (ASDs). A variety of agents that act at GABAARs s are used to terminate or prevent seizures. Many act at distinct receptor sites determined by the subunit composition of the holoreceptor. For the benzodiazepines, barbiturates, and loreclezole, actions at the GABAAR are the primary or only known mechanism of antiseizure action. For topiramate, felbamate, retigabine, losigamone and stiripentol, GABAAR modulation is one of several possible antiseizure mechanisms. Allopregnanolone, a progesterone metabolite that enhances GABAAR function, led to the development of ganaxolone. Other agents modulate GABAergic "tone" by regulating the synthesis, transport or breakdown of GABA. GABAAR efficacy is also affected by the transmembrane chloride gradient, which changes during development and in chronic epilepsy. This may provide an additional target for "GABAergic" ASDs. GABAAR subunit changes occur both acutely during status epilepticus and in chronic epilepsy, which alter both intrinsic GABAAR function and the response to GABAAR-acting ASDs. Manipulation of subunit expression patterns or novel ASDs targeting the altered receptors may provide a novel approach for seizure prevention.
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Affiliation(s)
- L John Greenfield
- Dept. of Neurology, University of Arkansas for Medical Sciences, 4301W. Markham St., Slot 500, Little Rock, AR 72205, United States.
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Allosteric modulation of GABA(A) receptor subtypes:effects on visual recognition and visuospatial working memory in rhesus monkeys [corrected]. Neuropsychopharmacology 2013; 38:2315-25. [PMID: 23722241 PMCID: PMC3773684 DOI: 10.1038/npp.2013.137] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 05/21/2013] [Accepted: 05/21/2013] [Indexed: 11/08/2022]
Abstract
Non-selective positive allosteric modulators (PAMs) of GABAA receptors (GABAARs) are known to impair anterograde memory. The role of the various GABAAR subtypes in the memory-impairing effects of non-selective GABAAR PAMs has not been fully elucidated. The current study assessed, in rhesus monkeys, effects of modulation of α1, α2/3, and α5GABAARs on visual recognition and spatial working memory using delayed matching-to-sample (DMTS) and self-ordered spatial search (SOSS) procedures, respectively. The DMTS procedure (n=8) involved selecting a previously presented 'sample' image from a set of multiple images presented after a delay. The SOSS procedure (n=6) involved touching a number of boxes without repeats. The non-selective GABAAR PAM triazolam and the α1GABAA preferential PAMS zolpidem and zaleplon reduced accuracy in both procedures, whereas the α5GABAA preferential PAMs SH-053-2'F-R-CH3 and SH-053-2'F-S-CH3, and the α2/3GABAA preferential PAM TPA023B were without effects on accuracy or trial completion. The low-efficacy α5GABAAR negative allosteric modulator (NAM) PWZ-029 slightly increased only DMTS accuracy, whereas the high-efficacy α5GABAAR NAMs RY-23 and RY-24 did not affect accuracy under either procedure. Finally, the slopes of the accuracy dose-effect curves for triazolam, zolpidem, and zaleplon increased with box number in the SOSS procedure, but were equivalent across DMTS delays. The present results suggest that (1) α1GABAARs, compared with α2/3 and α5GABAARs, are primarily involved in the impairment, by non-selective GABAAR PAMs, of visual recognition and visuospatial working memory in nonhuman primates; and (2) relative cognitive impairment produced by positive modulation of GABAARs increases with number of locations to be remembered, but not with the delay for remembering.
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Tonkiss J, Shultz PL, Bonnie KE, Hudson JL, Duran P, Galler JR. Spatial Learning Deficits Induced by Muscimol and CL218,872: Lack of Effect of Prenatal Malnutrition. Nutr Neurosci 2013; 6:379-87. [PMID: 14744042 DOI: 10.1080/10284150310001624200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The sensitivity of prenatal protein malnourished rats to the amnestic properties of the direct GABAA receptor agonist muscimol and the selective benzodiazepine (BZ) receptor agonist, CL218,872, was studied in the male offspring of rats provided with a protein deficient diet (6% casein) for 5 weeks prior to mating and throughout pregnancy. At postnatal day 90, rats were tested during acquisition of the submerged platform version of the Morris water maze task using four systemic doses of muscimol (0.1, 0.3, 1.0 and 1.8 mg/kg i.p.) or three systemic doses of CL218,872 (1.0, 3.2, and 5.6 mg/kg i.p.). In a dose dependent manner both drugs impaired acquisition of the task and impaired accuracy of the search pattern on the probe trial (platform removed). However, neither drug dissociated the performance of the two nutritional groups. These data are important in light of previous findings of differential behavioral effects of the non-specific BZ agonist, chlordiazepoxide (CDP), on spatial learning and on drug discrimination in prenatally malnourished rats and in the context of previous findings of reduced sensitivity to the anxiolytic effects of non-specific BZ receptor agonists across a wide variety of models of malnutrition. The present findings also support the concept that prenatal malnutrition does not affect the global functioning of the GABAA receptor, but fundamentally alters the way in which a subset of GABAA receptors (i.e. those containing the alpha2, alpha3 and/or the alpha5 but not the alpha1 subunit) is modulated by BZs.
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Affiliation(s)
- J Tonkiss
- Center for Behavioral Development and Mental Retardation, M923, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118, USA.
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Ghisdal P, Noel N, Pacico N, Martini M, Foerch P, Hanon E, Wolff C. Determining the Relative Efficacy of Positive Allosteric Modulators of the GABAA Receptor. ACTA ACUST UNITED AC 2013; 19:462-7. [DOI: 10.1177/1087057113501555] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Gamma amino butyric acid receptors (GABA) are major therapeutic targets for the development of drugs in neurological and psychiatric disorders. The new generation of GABAA modulators is targeting subtype selectivity and low/partial efficacy on the receptor to potentially overcome the adverse effects described for drugs with full agonist profile. We evaluated a screening approach to measure the relative efficacy of GABAA positive allosteric modulators (PAM) using automated patch clamp and fluorescence membrane potential assays. We determined that the use of an internal comparator (zolpidem), tested on each cell in parallel to the test compound, provides a reliable approach to measure and compare the relative efficacy of PAM ligands. Patch clamp recordings on recombinant GABAA receptors, using a multiple drug addition protocol, allows us to rank PAM ligands with different levels of efficacies. We observed that fluorescence membrane potential assays are not predictive of the relative efficacies of GABAA PAM ligands.
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Fischer BD, Teixeira LP, van Linn ML, Namjoshi OA, Cook JM, Rowlett JK. Role of gamma-aminobutyric acid type A (GABAA) receptor subtypes in acute benzodiazepine physical dependence-like effects: evidence from squirrel monkeys responding under a schedule of food presentation. Psychopharmacology (Berl) 2013; 227:347-54. [PMID: 23354533 PMCID: PMC3637862 DOI: 10.1007/s00213-013-2975-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 12/19/2012] [Indexed: 11/25/2022]
Abstract
RATIONALE Assays of schedule-controlled responding can be used to characterize the pharmacology of benzodiazepines and other GABAA receptor modulators, and are sensitive to changes in drug effects that are related to physical dependence. OBJECTIVE The present study used this approach to investigate the role of GABAA receptor subtypes in mediating dependence-like effects following benzodiazepine administration. METHODS Squirrel monkeys (n = 6) were trained on a fixed-ratio schedule of food reinforcement. Initially, the response rate-decreasing effects of chlordiazepoxide (0.1-10 mg/kg; nonselective GABAA receptor agonist), zolpidem (0.032-1.0 mg/kg; α1 subunit-containing GABAA subtype-preferring agonist), and HZ-166 (0.1-10 mg/kg; functionally selective α2 and α3 subunit-containing GABAA receptor agonist) were assessed. Next, acute dependence-like effects following single injections of chlordiazepoxide, zolpidem, and HZ-166 were assessed with flumazenil (0.1-3.2 mg/kg; nonselective GABAA receptor antagonist). Finally, acute dependence-like effects following zolpidem administration were assessed with βCCt and 3-PBC (0.1-3.2 mg/kg and 0.32-10 mg/kg, respectively; α1 subunit-containing GABAA receptor antagonists). RESULTS Chlordiazepoxide, zolpidem, and HZ-166 produced dose- and time-dependent decreases in response rates, whereas flumazenil, βCCT, and 3-PBC were ineffective. After the drug effects waned, flumazenil produced dose-dependent decreases in response rates following administration of 10 mg/kg chlordiazepoxide and 1.0 mg/kg zolpidem, but not following any dose of HZ-166. Further, both βCCT and 3-PBC produced dose-dependent decreases in response rates when administered after 1.0 mg/kg zolpidem. CONCLUSIONS These data raise the possibility that α1 subunit-containing GABAA receptors play a major role in physical dependence-related behaviors following a single injection of a benzodiazepine.
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Affiliation(s)
| | | | | | | | | | - James K. Rowlett
- Corresponding Author: , Phone: (508) 624-8036, Fax: (508) 624-8197
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Huot P, Johnston TH, Koprich JB, Fox SH, Brotchie JM. The Pharmacology of l-DOPA-Induced Dyskinesia in Parkinson’s Disease. Pharmacol Rev 2013; 65:171-222. [DOI: 10.1124/pr.111.005678] [Citation(s) in RCA: 233] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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Halas CJ. Cost-effectiveness of eszopiclone for the treatment of chronic insomnia. Expert Rev Pharmacoecon Outcomes Res 2012; 7:9-17. [PMID: 20528426 DOI: 10.1586/14737167.7.1.9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Eszopiclone (Lunesta) is the first hypnotic to receive US FDA approval for the long-term treatment of chronic insomnia. This novel nonbenzodiazepine hypnotic provides another option for patients with sleep disorders by inducing rapid-sleep onset and sleep maintenance. The drug is effective and well tolerated in adult patients with insomnia. Eszopiclone is more expensive than some other nonbenzodiazepine hypnotics (zaleplon, immediate release zolpidem) and benzodiazepine hypnotics, and much less expensive than controlled-release zolpidem. It is unclear whether or not the cost of eszopiclone will be offset owing to its side-effect profile and tolerability, since pharmacoeconomic studies are lacking.
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Affiliation(s)
- Cynthia J Halas
- Penn State Milton S. Hershey Medical Center, 500 University Drive Hershey, PA 17033, USA.
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Skolnick P. Anxioselective anxiolytics: on a quest for the Holy Grail. Trends Pharmacol Sci 2012; 33:611-20. [PMID: 22981367 DOI: 10.1016/j.tips.2012.08.003] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 08/17/2012] [Accepted: 08/20/2012] [Indexed: 01/01/2023]
Abstract
The discovery of benzodiazepine receptors provided the impetus to discover and develop anxioselective anxiolytics ('Valium without the side effects'). The market potential for an anxioselective based on the γ-aminobutyric acid A (GABA(A)) receptor resulted in clinical trials of multiple compounds. In contrast to the anxioselective profile displayed in preclinical models, compounds such as bretazenil, TPA023, and MRK 409 produced benzodiazepine-like side effects (sedation, dizziness) in Phase I studies, whereas alpidem and ocinaplon exhibited many of the characteristics of an anxioselective in the clinic. Alpidem was briefly marketed for the treatment of anxiety, but was withdrawn because of liver toxicity. Reversible elevations in liver enzymes halted development of ocinaplon in Phase III. The clinical profiles of these two molecules demonstrate that it is possible to develop GABA(A) receptor-based anxioselectives. However, despite the formidable molecular toolbox at our disposal, we are no better informed about the GABA(A) receptors responsible for an anxioselective profile in the clinic. Here, I discuss the evolution of a quest, spanning four decades, for molecules that retain the rapid and robust anti-anxiety actions of benzodiazepines without the side effects that limit their usefulness.
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Affiliation(s)
- Phil Skolnick
- Division of Pharmacotherapies and Medical Consequences of Drug Abuse, National Institute on Drug Abuse, National Institutes of Health, 6001 Executive Boulevard, Suite 4123, Bethesda, MD 20892, USA.
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Fung SJ, Xi M, Zhang J, Sampogna S, Chase MH. Apnea produces excitotoxic hippocampal synapses and neuronal apoptosis. Exp Neurol 2012; 238:107-13. [PMID: 22921462 DOI: 10.1016/j.expneurol.2012.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/27/2012] [Accepted: 08/03/2012] [Indexed: 12/20/2022]
Abstract
Obstructive sleep apnea (OSA) results in the degeneration of neurons in the hippocampus that eventuates in neurocognitive deficits. We were therefore interested in determining the effects of apnea on monosynaptic excitatory processes in a hippocampal pathway (cornu ammonis 3-cornu ammonis 1, CA3-CA1) that has been shown to mediate the processing of cognitive information. In addition, to substantiate an anatomical basis for the cognitive dysfunction that occurs in OSA patients, we examined the effects of apnea with respect to neurodegenerative changes (apoptosis) in the same hippocampal pathway. In order to determine the effects of apnea, an automated system for the generation and analysis of single and recurrent periods of apnea was developed. Utilizing this system, the field excitatory postsynaptic potential (fEPSP) generated by pyramidal neurons in the CA1 region of the hippocampus was monitored in α-chloralose anesthetized rats following stimulation of glutamatergic afferents in the CA3 region. A stimulus-response (input-output) curve for CA3-CA1 synaptic activity was determined. In addition, a paired-pulse paradigm was employed to evaluate, electrophysiologically, the presynaptic release of glutamate. Changes in the synaptic efficacy were assessed following single episodes of apnea induced by ventilatory arrest (60 to 80 s duration, mean=72 s; mean oxygen desaturation was 53% of normoxia level). Apnea resulted in a significant potentiation of the amplitude (mean=126%) and slope (mean=117%) of the baseline CA1 fEPSP. This increase in the fEPSP was accompanied by a significant decrease in the amplitude (71%) and slope (81%) of normalized paired-pulse facilitation (PPF) ratios. Since the potentiation of the fEPSP is inversely proportional to changes in PPF ratio, the potentiated fEPSP accompanied by the reduced PPF reveals that apnea produces an abnormal increase in the preterminal release of glutamate that results in the over-activation (and calcium overloading) of hippocampal CA1 neurons. Thus, we conclude that individual episodes of apnea result in the development of excitotoxic processes in the hippocampal CA3-CA1 pathway that is critically involved in the processing of cognitive information. Morphologically, the deleterious effect of recurrent apnea was substantiated by the finding of apoptosis in CA1 neurons of apneic (but not normoxic) animals.
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Affiliation(s)
- Simon J Fung
- VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA.
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Masneuf S, Buetler J, Koester C, Crestani F. Role of α1- and α2-GABA(A) receptors in mediating the respiratory changes associated with benzodiazepine sedation. Br J Pharmacol 2012; 166:339-48. [PMID: 22044283 DOI: 10.1111/j.1476-5381.2011.01763.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND AND PURPOSE The molecular substrates underlying the respiratory changes associated with benzodiazepine sedation are unknown. We examined the effects of different doses of diazepam and alprazolam on resting breathing in wild-type (WT) mice and clarified the contribution of α1- and α2-GABA(A) receptors, which mediate the sedative and muscle relaxant action of diazepam, respectively, to these drug effects using point-mutated mice possessing either α1H101R- or α2H101R-GABA(A) receptors insensitive to benzodiazepine. EXPERIMENTAL APPROACH Room air breathing was monitored using whole-body plethysmography. Different groups of WT mice were injected i.p. with diazepam (1-100 mg·kg(-1) ), alprazolam (0.3, 1 or 3 mg·kg(-1) ) or vehicle. α1H101R and α2H101R mice received 1 or 10 mg·kg(-1) diazepam or 0.3 or 3 mg·kg(-1) alprazolam. Respiratory frequency, tidal volume, time of expiration and time of inspiration before and 20 min after drug injection were analysed. KEY RESULTS Diazepam (10 mg·kg(-1) ) decreased the time of expiration, thereby increasing the resting respiratory frequency, in WT and α2H101R mice, but not in α1H101R mice. The time of inspiration was shortened in WT and α1H101R mice, but not in α2H101R mice. Alprazolam (1-3 mg·kg(-1) ) stimulated the respiratory frequency by shortening expiration and inspiration duration in WT mice. This tachypnoeic effect was partially conserved in α1H101R mice while absent in α2H101R mice. CONCLUSIONS AND IMPLICATIONS These results identify a specific role for α1-GABA(A) receptors and α2-GABA(A) receptors in mediating the shortening by benzodiazepines of the expiratory and inspiratory phase of resting breathing respectively.
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Affiliation(s)
- S Masneuf
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland
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Lundahl J, Deacon S, Maurice D, Staner L. EEG spectral power density profiles during NREM sleep for gaboxadol and zolpidem in patients with primary insomnia. J Psychopharmacol 2012; 26:1081-7. [PMID: 22057018 DOI: 10.1177/0269881111424457] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
There is significant interest in the functional significance and the therapeutic value of slow-wave sleep (SWS)-enhancing drugs. A prerequisite for studies of the functional differences is characterization of the electroencephalography (EEG) spectra following treatment in relevant patients. We evaluate for the first time gaboxadol and zolpidem treatments in insomniac patients using power spectra analysis. We carried out two randomized, double-blind, crossover studies. Study 1, 38 patients received gaboxadol 10 mg and 20 mg and zolpidem 10 mg; study 2, 23 patients received gaboxadol 5 mg and 15 mg. Treatments were administered during two nights and compared with placebo. Gaboxadol 10, 15 and 20 mg enhanced slow-wave activity (SWA) and theta power. In 1 Hz bins gaboxadol 10 and 20 mg enhanced power up to 9 Hz. In study 2, 15 mg gaboxadol showed a similar effect pattern. Zolpidem suppressed theta and alpha power, and increased sigma power, with no effect on SWA. In the 1 Hz bins zolpidem suppressed power between 5-10 Hz. Gaboxadol dose-dependently increased SWA and theta power in insomniac patients. In contrast, zolpidem did not affect SWA, reduced theta and alpha activity and enhanced sigma power. EEG spectral power differences may be consequences of the different mechanisms of action for zolpidem and the SWS-enhancing agent, gaboxadol.
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Affiliation(s)
- Jonas Lundahl
- ICR Paediatric Neuro-Psychiatry, H. Lundbeck A/S, Ottiliavej 9, Valby, Copenhagen, Denmark.
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Abstract
INTRODUCTION Insomnia is one of the most prevalent sleep disorders in developed countries, being surpassed only by chronic sleep deprivation. Patients with insomnia tend to have an altered quality of life, impaired daytime functioning and an increased risk of work accidents and motor vehicle crashes. Insomnia is commonly associated with chronic medical conditions, metabolic illnesses and mental disorders (such as depression and anxiety), with which there is a dual, reciprocal relationship. AREAS COVERED This paper focuses on current pharmacotherapy options for the treatment of insomnia, particularly benzodiazepine receptor agonists, which nowadays represent the mainstay of hypnotic therapy. The melatonin receptor antagonist, ramelteon, is reviewed (an alternative for some patients with only sleep-onset difficulty), as are sedating antidepressants, which are commonly used 'off-label' to treat insomnia, despite limited efficacy data and potential significant safety concerns. Orexin (OX) antagonists are also discussed, especially those that block OX2 or both OX1 and OX2 receptors, as these are the most promising new agents for the treatment of insomnia, with encouraging results in preliminary clinical trials. EXPERT OPINION Research to evaluate and formulate treatments for insomnia is often complicated by the fact that insomnia is usually of multifactorial etiology. Understanding the molecular and receptor mechanisms involved in promoting sleep in varied disorders could provide future approaches in new drug development. In the long term, more randomized controlled trials are needed to assess both short-term and long-term effects of these medications and their efficacy in comorbid diseases that affect sleep quality or quantity.
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Affiliation(s)
- Octavian C Ioachimescu
- Emory School of Medicine, Atlanta VA Medical Center, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Atlanta, GA, USA
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Foda NH, Ali SM. Zolpidem tartrate. PROFILES OF DRUG SUBSTANCES, EXCIPIENTS, AND RELATED METHODOLOGY 2012; 37:413-38. [PMID: 22469325 DOI: 10.1016/b978-0-12-397220-0.00011-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Nagwa H Foda
- Department of Pharmaceutical Chemistry, King Saud University, Riyadh, Kingdom of Saudi Arabia
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Atack JR, Hallett DJ, Tye S, Wafford KA, Ryan C, Sanabria-Bohórquez SM, Eng WS, Gibson RE, Burns HD, Dawson GR, Carling RW, Street LJ, Pike A, De Lepeleire I, Van Laere K, Bormans G, de Hoon JN, Van Hecken A, McKernan RM, Murphy MG, Hargreaves RJ. Preclinical and clinical pharmacology of TPA023B, a GABAA receptor α2/α3 subtype-selective partial agonist. J Psychopharmacol 2011; 25:329-44. [PMID: 20156926 DOI: 10.1177/0269881109354928] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In the accompanying paper we describe how MRK-409 unexpectedly produced sedation in man at relatively low levels of GABA(A) receptor occupancy (∼10%). Since it was not clear whether this sedation was mediated via the α2/α3 or α1 GABA(A) subtype(s), we characterized the properties of TPA023B, a high-affinity imidazotriazine which, like MRK-409, has partial agonist efficacy at the α2 and α3 subtype but is an antagonist at the α1 subtype, at which MRK-409 has weak partial agonism. TPA023B gave dose- and time-dependent occupancy of rat brain GABA(A) receptors as measured using an in vivo [(3)H]flumazenil binding assay, with 50% occupancy corresponding to a respective dose and plasma drug concentration of 0.09 mg/kg and 19 ng/mL, the latter of which was similar to that observed in mice (25 ng/mL) and comparable to values obtained in baboon and man using [(11)C]flumazenil PET (10 and 5.8 ng/mL, respectively). TPA023B was anxiolytic in rodent and primate (squirrel monkey) models of anxiety (elevated plus maze, fear-potentiated startle, conditioned suppression of drinking, conditioned emotional response) yet had no significant effects in rodent or primate assays of ataxia and/or myorelaxation (rotarod, chain-pulling, lever pressing), up to doses (10 mg/kg) corresponding to occupancy of greater than 99%. In man, TPA023B was well tolerated at a dose (1.5 mg) that produced occupancy of >50%, suggesting that the sedation previously seen with MRK-409 is due to the partial agonist efficacy of that compound at the α1 subtype, and highlighting the importance of antagonist efficacy at this particular GABA(A) receptor population for avoiding sedation in man.
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Affiliation(s)
- J R Atack
- Neuroscience Research Centre, Merck Sharp & Dohme Research Laboratories, Harlow, UK.
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Asai Y, Ikoma Y, Takano A, Maeda J, Toyama H, Yasuno F, Ichimiya T, Ito H, Suhara T. Quantitative analyses of [¹¹C]Ro15-4513 binding to subunits of GABAA/benzodiazepine receptor in the living human brain. Nucl Med Commun 2011; 30:872-80. [PMID: 19657305 DOI: 10.1097/mnm.0b013e32833019bf] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Gamma-aminobutyric acid (GABA)A/benzodiazepine (BZ) receptor chloride channel consists of several subunits. The diversity of the α subunits results in the various ligand selectivity and functionally different properties of the GABAA/BZ receptor. Although [¹¹C] Ro15-4513 is reported to be a radioligand that has relatively high affinity for α5 subunit-containing GABAA/BZ receptor, it remained to be evaluated fully. AIM The aim of this study was to evaluate the quantitative analyses of [¹¹C]Ro15-4513 in the living human brain. METHODS Positron emission tomography examinations were performed in eight healthy male volunteers after intravenous injection of [¹¹C]Ro15-4513. Kinetic analysis of data was performed with the two-compartment and three-compartment models using arterial input function. Linear graphical analysis and the simplified reference tissue model analysis (SRTM) were also performed using pons as a reference region. In a simulation study, the effects of noise to the estimation of binding potentials were evaluated. RESULTS The accumulation of [¹¹C]Ro15-4513 in the limbic system was relatively higher than in other cortex. The bindings were well described by the three-compartment model in the regions with specific binding. Binding potentials obtained from the graphical method and SRTM correlated well with those obtained from the three-compartment model. In the simulation study, estimated parameters from SRTM were less affected by noise compared with those from the graphical method. CONCLUSION The reference tissue methods using pons as a reference region can be used for quantitative analysis of [¹¹C]Ro15-4513 binding. SRTM seemed less susceptible to noise than does graphical analysis.
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Affiliation(s)
- Yoshiyuki Asai
- Molecular Neuroimaging Group, Molecular Imaging Center, National Institute of Radiological Sciences, Chiba, Japan
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Hambrecht-Wiedbusch VS, Gauthier EA, Baghdoyan HA, Lydic R. Benzodiazepine receptor agonists cause drug-specific and state-specific alterations in EEG power and acetylcholine release in rat pontine reticular formation. Sleep 2010; 33:909-18. [PMID: 20614851 PMCID: PMC2894433 DOI: 10.1093/sleep/33.7.909] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
STUDY OBJECTIVES Benzodiazepine (BDZ) and non-benzodiazepine (NBDZ) hypnotics enhance GABAergic transmission and are widely used for the treatment of insomnia. In the pontine reticular formation (PRF), GABA inhibits rapid eye movement (REM) sleep and acetylcholine (ACh) release. No previous studies have characterized the effects of BDZ and NBDZ hypnotics on ACh release in the PRF. This study tested 2 hypotheses: (1) that microdialysis delivery of zolpidem, eszopiclone, and diazepam to rat PRF alters ACh release in PRF and electroencephalographic (EEG) delta power and (2) that intravenous (i.v.) administration of eszopiclone to non-anesthetized rat alters ACh release in the PRF, sleep, and EEG delta power. DESIGN A within- and between-groups experimental design. SETTING University of Michigan. PATIENTS OR PARTICIPANTS Adult male Crl:CD*(SD) (Sprague-Dawley) rats (n = 57). INTERVENTIONS In vivo microdialysis of the PRF in rats anesthetized with isoflurane was used to derive the concentration-response effects of zolpidem, eszopiclone, and diazepam on ACh release. Chronically instrumented rats were used to quantify the effects of eszopiclone (3 mg/kg, i.v.) on ACh release in the PRF, sleep-wake states, and cortical EEG power. MEASUREMENTS AND RESULTS ACh release was significantly increased by microdialysis delivery to the PRF of zolpidem and eszopiclone but not diazepam. EEG delta power was increased by zolpidem and diazepam but not by eszopiclone administered to the PRF. Eszopiclone (i.v.) decreased ACh release in the PRF of both anesthetized and non-anesthetized rats. Eszopiclone (i.v.) prevented REM sleep and increased EEG delta power. CONCLUSION The concentration-response data provide the first functional evidence that multiple GABA(A) receptor subtypes are present in rat PRF. Intravenously administered eszopiclone prevented REM sleep, decreased ACh release in the PRF, and increased EEG delta power. The effects of eszopiclone are consistent with evidence that ACh release in the PRF is lower during NREM sleep than during REM sleep, and with data showing that cholinergic stimulation of the PRF activates the cortical EEG.
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Affiliation(s)
| | | | - Helen A. Baghdoyan
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan
| | - Ralph Lydic
- Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan
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49
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Ramerstorfer J, Furtmüller R, Vogel E, Huck S, Sieghart W. The point mutation gamma 2F77I changes the potency and efficacy of benzodiazepine site ligands in different GABAA receptor subtypes. Eur J Pharmacol 2010; 636:18-27. [PMID: 20303942 PMCID: PMC7615656 DOI: 10.1016/j.ejphar.2010.03.015] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 02/17/2010] [Accepted: 03/03/2010] [Indexed: 11/26/2022]
Abstract
Benzodiazepine site agonists or inverse agonists enhance or reduce gamma-aminobutyric acid(A) (GABA(A)) receptor-mediated inhibition of neurons, respectively. Recently, it was demonstrated that the point mutation gamma 2F77I causes a drastic change in the affinity of a variety of benzodiazepine agonists or inverse agonists in receptor binding studies. Here we investigated the potency and efficacy of 10 benzodiazepine site ligands from 6 structural classes in wild-type and gamma 2F77I point mutated recombinant GABA(A) receptors composed of alpha 1 beta 3 gamma 2, alpha 2 beta 3 gamma 2, alpha 3 beta 3 gamma 2, alpha 4 beta 3 gamma 2, alpha 5 beta 3 gamma 2, and alpha 6 beta 3 gamma 2 subunits. Results indicate that the effects of the benzodiazepine site ligands zolpidem, zopiclone, Cl218872, L-655,708 and DMCM were nearly completely eliminated in all mutated receptors up to a 1 microM concentration. The effects of bretazenil, Ro15-1788 or abecarnil were eliminated in some, but not all mutated receptors, suggesting that the gamma 2F77I mutation differentially influences the actions of these ligands in different receptor subtypes. In addition, this point mutation also influences the efficacy of diazepam for enhancing GABA-induced chloride flux, suggesting that the amino acid residue gamma 2F77 might also be involved in the transduction of the effect of benzodiazepines from binding to gating. The application of these drugs in a novel mouse model is discussed.
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Affiliation(s)
- Joachim Ramerstorfer
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Roman Furtmüller
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Elisabeth Vogel
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Sigismund Huck
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090 Vienna, Austria
| | - Werner Sieghart
- Department of Biochemistry and Molecular Biology, Center for Brain Research, Medical University Vienna, Spitalgasse 4, 1090 Vienna, Austria
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Wang MD, Rahman M, Johansson IM, Bäckström T. Agonist function of the recombinant alpha 4 beta 3 delta GABAA receptor is dependent on the human and rat variants of the alpha 4-subunit. Clin Exp Pharmacol Physiol 2010; 37:662-9. [PMID: 20337660 DOI: 10.1111/j.1440-1681.2010.05374.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. It is known that the alpha(4)-subunit is likely to occur in the brain predominantly in alpha(4)beta(3)delta receptors at extrasynaptic sites. Recent studies have revealed that the alpha(1)-, alpha(4)-, gamma(2)- and delta-subunits may colocalize extrasynaptically in dentate granule cells of the hippocampus. In the present study, we characterized a series of recombinant GABA(A) receptors containing human (H) and rat (R) alpha(1)/alpha(4)-, beta(2)/beta(3)- and gamma(2S)/delta-subunits in Xenopus oocytes using the two-electrode voltage-clamp technique. 2. Both H alpha(1)beta(3)delta and H alpha(4)beta(3)gamma(2S) receptors were sensitive to activation by GABA and pentobarbital. Contrary to earlier findings that the alpha(4)beta(3)delta combination was more sensitive to agonist action than the alpha(4)beta(3)gamma(2S) receptor, we observed extremely small GABA- and pentobarbital-activated currents at the wild-type H alpha(4)beta(3)delta receptor. However, GABA and pentobarbital activated the wild-type R alpha(4)beta(3)delta receptor with high potency (EC(50) = 0.5 +/- 0.7 and 294 +/- 5 micromol/L, respectively). 3. Substituting the H alpha(4) subunit with R alpha(4) conferred a significant increase in activation on the GABA and pentobarbital site in terms of reduced EC(50) and increased I(max). When the H alpha(4) subunit was combined with the R beta(3) and R delta subunit in a heteropentameric form, the amplitude of GABA- and pentobarbital-activated currents increased significantly compared with the wild-type H alpha(4)beta(3)delta receptor. 4. Thus, the results indicate that the R alpha(4)beta(3)delta, H alpha(1)beta(3)delta and H alpha(4)beta(3)gamma(2S) combinations may contribute to functions of extrasynaptic GABA(A) receptors. The presence of the R alpha(4) subunit at recombinant GABA(A) receptors containing the delta-subunit is a strong determinant of agonist action. The recombinant H alpha(4)beta(3)delta receptor is a less sensitive subunit composition in terms of agonist activation.
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Affiliation(s)
- Ming-De Wang
- Department of Clinical Science, Umeå Neurosteroid Research Center, Obstetrics and Gynecology, Umeå University, Umeå, Sweden.
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