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Li L, Wu X, Gong J, Wang Z, Dai W, Qiu L, Zuo H, Yi M, Yuan H, Hu M, Gao Z, Tian F. Activation of GABA type A receptor is involved in the anti-insomnia effect of Huanglian Wendan Decoction. Front Pharmacol 2024; 15:1389768. [PMID: 38846089 PMCID: PMC11153716 DOI: 10.3389/fphar.2024.1389768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 05/01/2024] [Indexed: 06/09/2024] Open
Abstract
Huanglian Wendan Decoction (HWD) is a traditional Chinese medicine (TCM) prescribed to patients diagnosed with insomnia, which can achieve excellent therapeutic outcomes. As positively modulating the γ-aminobutyric acid (GABA) type A receptors (GABAARs) is the most effective strategy to manage insomnia, this study aimed to investigate whether the activation of GABAARs is involved in the anti-insomnia effect of HWD. We assessed the metabolites of HWD using LC/MS and the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database and tested the pharmacological activity in vitro and in vivo using whole-cell patch clamp and insomnia zebrafish model. In HEK293 cells expressing α1β3γ2L GABAARs, HWD effectively increased the GABA-induced currents and could induce GABAAR-mediated currents independent of the application of GABA. In the LC-MS (QToF) assay, 31 metabolites were discovered in negative ion modes and 37 metabolites were found in positive ion modes, but neither three selected active metabolites, Danshensu, Coptisine, or Dihydromyricetin, showed potentiating effects on GABA currents. 62 active metabolites of the seven botanical drugs were collected based on the TCMSP database and 19 of them were selected for patch-clamp verification according to the virtual docking simulations and other parameters. At a concentration of 100 μM, GABA-induced currents were increased by (+)-Cuparene (278.80% ± 19.13%), Ethyl glucoside (225.40% ± 21.77%), and β-Caryophyllene (290.11% ± 17.71%). In addition, (+)-Cuparene, Ethyl glucoside, and β-Caryophyllene could also serve as positive allosteric modulators (PAMs) and shifted the GABA dose-response curve (DRC) leftward significantly. In the PCPA-induced zebrafish model, Ethyl glucoside showed anti-insomnia effects at concentrations of 100 μM. In this research, we demonstrated that the activation of GABAARs was involved in the anti-insomnia effect of HWD, and Ethyl glucoside might be a key metabolite in treating insomnia.
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Affiliation(s)
- Liang Li
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, China
| | - Xiaorong Wu
- School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang, China
- Zhongshan Institute for Drug Discovery, Zhongshan, China
| | - Jili Gong
- School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang, China
- Zhongshan Institute for Drug Discovery, Zhongshan, China
| | - Zhuqiang Wang
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, China
| | - Weibo Dai
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, China
| | - Li Qiu
- Zhongshan Institute for Drug Discovery, Zhongshan, China
- School of Pharmacy, Zunyi Medical University, Zunyi, China
| | - Hongyuan Zuo
- Zhongshan Institute for Drug Discovery, Zhongshan, China
| | - Mengqin Yi
- Zhongshan Institute for Drug Discovery, Zhongshan, China
| | - Hui Yuan
- Zhongshan Institute for Drug Discovery, Zhongshan, China
- School of Pharmacy, Zunyi Medical University, Zunyi, China
| | - Mei Hu
- Pharmacology Laboratory, Zhongshan Traditional Chinese Medicine Hospital, Guangzhou University of Chinese Medicine, Zhongshan, China
- Zhongshan Institute for Drug Discovery, Zhongshan, China
| | - Zhaobing Gao
- School of Pharmaceutical Sciences, Guizhou Medical University, Guiyang, China
- Zhongshan Institute for Drug Discovery, Zhongshan, China
- School of Pharmacy, Zunyi Medical University, Zunyi, China
| | - Fuyun Tian
- Zhongshan Institute for Drug Discovery, Zhongshan, China
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Vivek K, Karagozlu Z, Erridge S, Holvey C, Coomber R, Rucker JJ, Weatherall MW, Sodergren MH. UK Medical Cannabis Registry: Assessment of clinical outcomes in patients with insomnia. Brain Behav 2024; 14:e3410. [PMID: 38337193 PMCID: PMC10858318 DOI: 10.1002/brb3.3410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 10/04/2023] [Accepted: 01/09/2024] [Indexed: 02/12/2024] Open
Abstract
INTRODUCTION The primary aim of this study was to assess changes in sleep-specific health-related quality of life (HRQoL) for those prescribed cannabis-based medicinal products (CBMPs) for insomnia. METHODS A case series of UK patients with insomnia was analyzed. Primary outcomes were changes in the Single-Item Sleep-Quality Scale (SQS), Generalized Anxiety Disorder-7 (GAD-7), and EQ-5D-5L at up to 6 months from baseline. Statistical significance was identified as a p value < .050. RESULTS 61 patients were included in the analysis. There was an improvement in the SQS from baseline at 1, 3, and 6 months (p < .001). There were also improvements in the EQ-5D-5L Index value and GAD-7 at 1, 3, and 6 months (p < .050). There were 28 (45.9%) adverse events recorded by 8 patients (13.1%). There were no life-threatening/disabling adverse events. CONCLUSION Patients with insomnia experienced an improvement in sleep quality following the initiation of CBMPs in this medium-term analysis. Fewer than 15% of participants reported one or more adverse events. However, due to the limitations of the study design, further investigation is required before definitive conclusions can be drawn on the efficacy of CBMPs in treating insomnia.
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Affiliation(s)
- Kavyesh Vivek
- Imperial College Medical Cannabis Research Group, Department of Surgery and CancerImperial College LondonLondonUK
| | - Zekiye Karagozlu
- Imperial College Medical Cannabis Research Group, Department of Surgery and CancerImperial College LondonLondonUK
| | - Simon Erridge
- Imperial College Medical Cannabis Research Group, Department of Surgery and CancerImperial College LondonLondonUK
- Department of MedicineCuraleaf ClinicLondonUK
| | - Carl Holvey
- Department of MedicineCuraleaf ClinicLondonUK
| | - Ross Coomber
- Department of MedicineCuraleaf ClinicLondonUK
- Department of Trauma and OrthopaedicsSt. George's Hospital NHS TrustLondonUK
| | - James J. Rucker
- Department of MedicineCuraleaf ClinicLondonUK
- Department of Psychological MedicineKings College LondonLondonUK
- National and Specialist Tertiary Referrals Affective Disorders ServiceSouth London & Maudsley NHS Foundation TrustLondonUK
| | - Mark W. Weatherall
- Department of MedicineCuraleaf ClinicLondonUK
- Department of NeurologyBuckinghamshire Healthcare NHS TrustAmershamUK
| | - Mikael H Sodergren
- Imperial College Medical Cannabis Research Group, Department of Surgery and CancerImperial College LondonLondonUK
- Department of MedicineCuraleaf ClinicLondonUK
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Borghese CM, Goldschen-Ohm MP. State-dependent energetics of GABA A receptor modulators. Biophys J 2024:S0006-3495(24)00093-6. [PMID: 38303510 DOI: 10.1016/j.bpj.2024.01.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2023] [Revised: 01/23/2024] [Accepted: 01/29/2024] [Indexed: 02/03/2024] Open
Affiliation(s)
- Cecilia M Borghese
- University of Texas at Austin, Department of Neuroscience, Austin, Texas
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Krystal AD. Insomnia medications: History, characteristics, and guidelines for optimal use in clinical practice. J Sleep Res 2023; 32:e14084. [PMID: 37940337 DOI: 10.1111/jsr.14084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 10/12/2023] [Indexed: 11/10/2023]
Abstract
This article reviews the history of insomnia pharmacotherapy, documenting the evolution that has occurred over time in the increasing availability of medications with novel mechanisms of action that more specifically target the neural systems that modulate sleep/wake function. This evolution provides an increasing capacity to improve the effectiveness of insomnia pharmacotherapy by allowing the selection of medications that specifically target the particular type of sleep difficulty present in each patient. As a result, they can achieve a therapeutic effect with fewer effects on aspects of brain function other than those needed to achieve benefit, thereby minimising adverse effects. The accumulated evidence-base is such that it can serve as the basis for a personalised insomnia pharmacotherapy paradigm. Here we outline a set of best-practice recommendations for how to carry out optimised personalised insomnia pharmacotherapy based on that evidence base in the hope that it will improve the treatment delivered to the many individuals suffering from insomnia.
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Affiliation(s)
- Andrew D Krystal
- Department of Psychiatry and Behavioral Sciences, University of California San Francisco, San Francisco, CA, USA
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5
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Zhu Y, Feng W, Kong Q, Sheng F, Li Z, Xu W, Li Q, Han Y, Wu X, Jia C, Guo J, Zhao Y. Evaluating the effects of S-ketamine on postoperative delirium in elderly patients following total hip or knee arthroplasty under intraspinal anesthesia: a single-center randomized, double-blind, placebo-controlled, pragmatic study protocol. Front Aging Neurosci 2023; 15:1298661. [PMID: 38099265 PMCID: PMC10720081 DOI: 10.3389/fnagi.2023.1298661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/14/2023] [Indexed: 12/17/2023] Open
Abstract
Introduction Postoperative delirium (POD) is an acute, transient brain disorder associated with decreased postoperative quality of life, dementia, neurocognitive changes, and mortality. A small number of trials have explored the role of S-ketamine in the treatment of POD due to its neuroprotective effects. Surprisingly, these trials have failed to yield supportive results. However, heterogeneity in delirium assessment methodologies, sample sizes, and outcome settings as well as deficiencies in S-ketamine use methods make the evidence provided by these studies less persuasive. Given the severe impact of POD on the health of elderly patients and the potential for S-ketamine to prevent it, we believe that designing a large sample size, and rigorous randomized controlled trial for further evaluation is necessary. Methods This is a single-center, randomized, double-blind, placebo-controlled, pragmatic study. Subjects undergoing total hip or knee arthroplasty will be randomized in a 1:1 ratio to intervention (n = 186) and placebo (n = 186) groups. This trial aims to explore the potential role of S-ketamine in the prevention of POD. Its primary outcome is the incidence of POD within 3 postoperative days. Secondary outcomes include the number of POD episodes, the onset and duration of POD, the severity and subtype of POD, pain scores and opioid consumption, sleep quality, clinical outcomes, and safety outcomes. Discussion To our knowledge, this is the first pragmatic study that proposes to use S-ketamine to prevent POD. We reviewed a large body of literature to identify potential preoperative confounding variables that may bias associations between the intervention and primary outcome. We will use advanced statistical methods to correct potential confounding variables, improving the test's power and external validity of test results. Of note, the patient population included in this trial will undergo intraspinal anesthesia. Although large, multicenter, randomized controlled studies have found no considerable difference in the effects of regional and general anesthesia on POD, patients receiving intraspinal anesthesia have less exposure to at-risk drugs, such as sevoflurane, propofol, and benzodiazepines, than patients receiving general anesthesia. At-risk drugs have been shown to negatively interfere with the neuroprotective effects of S-ketamine, which may be the reason for the failure of a large number of previous studies. There is currently a lack of randomized controlled studies evaluating S-ketamine for POD prevention, and our trial helps to fill a gap in this area.Trial registration: http://www.chictr.org.cn, identifier ChiCTR2300075796.
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Affiliation(s)
- Youzhuang Zhu
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Wei Feng
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Qinghan Kong
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Fang Sheng
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Zhichao Li
- Department of Anesthesiology, Cancer Hospital Chinese Academy of Medical Science, Beijing, China
| | - Weilong Xu
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Qun Li
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Yan Han
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Xiuyun Wu
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Changxin Jia
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
| | - Jie Guo
- Department of Anesthesiology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Yang Zhao
- Department of Anesthesiology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong Province, China
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6
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Horacek J, Janda R, Görnerova N, Jajcay L, Andrashko V. Several reasons why ketamine as a neuroplastic agent may have failed to prevent postoperative delirium: Implications for future protocols. Neurosci Lett 2023; 798:137095. [PMID: 36693556 DOI: 10.1016/j.neulet.2023.137095] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 12/14/2021] [Accepted: 01/19/2023] [Indexed: 01/22/2023]
Abstract
Ketamine exerts anti-inflammatory, neuroprotective and neuroplastic activity, therefore it may counteract the neurotoxic processes underlying postoperative delirium. However, the majority of studies in this field failed. We identified several pharmacological reasons why these studies may have failed, together with suggestions of how to remediate them. Among them, the interaction with intravenous general anesthetics exerting the opposite effect on GABA interneurons than ketamine may be of principal importance. We suggest biomarkers which may elucidate the influence of this interaction on the different steps of neuroplastic pathways. We hypothesize that administering ketamine before or after general anesthesia could both prevent the interactions and strengthen the effect of ketamine by timing surgery within the climax of ketamine-induced neuroplastic changes or by stabilizing AMPA receptors. It is vital to deal with these questions because the protocols of ongoing studies are based again on the administration of ketamine during general anesthesia (the major identified pitfall).
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Affiliation(s)
- Jiri Horacek
- National Institute of Mental Health, Klecany, Czech Republic; Third Faculty of Medicine, Charles University, Prague, Czech Republic.
| | - Robert Janda
- Intensive Care Unit, Karlovy Vary Regional Hospital, K. Vary, Czech Republic
| | - Natalie Görnerova
- National Institute of Mental Health, Klecany, Czech Republic; Third Faculty of Medicine, Charles University, Prague, Czech Republic
| | - Lucia Jajcay
- National Institute of Mental Health, Klecany, Czech Republic; Faculty of Electrical Engineering, Czech Technical University in Prague, Prague, Czech Republic
| | - Veronika Andrashko
- National Institute of Mental Health, Klecany, Czech Republic; Third Faculty of Medicine, Charles University, Prague, Czech Republic
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7
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Huang Z, Niu L. RNA aptamers for AMPA receptors. Neuropharmacology 2021; 199:108761. [PMID: 34509496 DOI: 10.1016/j.neuropharm.2021.108761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 08/07/2021] [Accepted: 08/19/2021] [Indexed: 12/16/2022]
Abstract
RNA aptamers are single-stranded RNA molecules, and they are selected against a target of interest so that they can bind to and modulate the activity of the target, such as inhibiting the target activity, with high potency and selectivity. Antagonists, such as RNA aptamers, acting on AMPA receptors, a major subtype of ionotropic glutamate receptors, are potential drug candidates for treatment of a number of CNS diseases that involve excessive receptor activation and/or elevated receptor expression. Here we review the approach to discover RNA aptamers targeting AMPA receptors from a random sequence library (∼1014 sequences) through a process called systematic evolution of ligands by exponential enrichment (SELEX). As compared with small-molecule compounds, RNA aptamers are a new class of regulatory agents with interesting and desirable pharmacological properties. Some AMPA receptor aptamers we have developed are presented in this review. The promises and challenges of translating RNA aptamers into potential drugs and treatment options are also discussed. This article is part of the special Issue on 'Glutamate Receptors - AMPA receptors'.
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Affiliation(s)
- Zhen Huang
- Chemistry Department, Center for Neuroscience Research, University at Albany, State University of New York (SUNY), Albany, NY, USA
| | - Li Niu
- Chemistry Department, Center for Neuroscience Research, University at Albany, State University of New York (SUNY), Albany, NY, USA.
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8
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Kim JJ, Hibbs RE. Direct Structural Insights into GABA A Receptor Pharmacology. Trends Biochem Sci 2021; 46:502-517. [PMID: 33674151 DOI: 10.1016/j.tibs.2021.01.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Revised: 01/08/2021] [Accepted: 01/25/2021] [Indexed: 12/18/2022]
Abstract
GABAA receptors are pentameric ligand-gated ion channels that mediate most fast neuronal inhibition in the brain. In addition to their important physiological roles, they are noteworthy in their rich pharmacology; prominent drugs used for anxiety, insomnia, and general anesthesia act through positive modulation of GABAA receptors. Direct structural information for how these drugs work was absent until recently. Efforts in structural biology over the past few years have revealed how important drug classes and natural products interact with the GABAA receptor, providing a foundation for studies in dynamics and structure-guided drug design. Here, we review recent developments in GABAA receptor structural pharmacology, focusing on subunit assemblies of the receptor found at synapses.
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Affiliation(s)
- Jeong Joo Kim
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Ryan E Hibbs
- Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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9
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Nors JW, Gupta S, Goldschen-Ohm MP. A critical residue in the α 1M2-M3 linker regulating mammalian GABA A receptor pore gating by diazepam. eLife 2021; 10:64400. [PMID: 33591271 PMCID: PMC7899671 DOI: 10.7554/elife.64400] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 02/15/2021] [Indexed: 01/29/2023] Open
Abstract
Benzodiazepines (BZDs) are a class of widely prescribed psychotropic drugs that modulate activity of GABAA receptors (GABAARs), neurotransmitter-gated ion channels critical for synaptic transmission. However, the physical basis of this modulation is poorly understood. We explore the role of an important gating domain, the α1M2–M3 linker, in linkage between the BZD site and pore gate. To probe energetics of this coupling without complication from bound agonist, we use a gain of function mutant (α1L9'Tβ2γ2L) directly activated by BZDs. We identify a specific residue whose mutation (α1V279A) more than doubles the energetic contribution of the BZD positive modulator diazepam (DZ) to pore opening and also enhances DZ potentiation of GABA-evoked currents in a wild-type background. In contrast, other linker mutations have little effect on DZ efficiency, but generally impair unliganded pore opening. Our observations reveal an important residue regulating BZD-pore linkage, thereby shedding new light on the molecular mechanism of these drugs.
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Affiliation(s)
- Joseph W Nors
- University of Texas at Austin, Department of Neuroscience, Austin, United States
| | - Shipra Gupta
- University of Texas at Austin, Department of Neuroscience, Austin, United States
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10
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Sarkar S, Choudhury S, Islam N, Chowdhury MSJH, Chowdhury MTI, Baker MR, Baker SN, Kumar H. Effects of Diazepam on Reaction Times to Stop and Go. Front Hum Neurosci 2020; 14:567177. [PMID: 33132880 PMCID: PMC7573484 DOI: 10.3389/fnhum.2020.567177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 08/31/2020] [Indexed: 01/13/2023] Open
Abstract
Introduction: The ability to stop the execution of a movement in response to an external cue requires intact executive function. The effect of psychotropic drugs on movement inhibition is largely unknown. Movement stopping can be estimated by the Stop Signal Reaction Time (SSRT). In a recent publication, we validated an improved measure of SSRT (optimum combination SSRT, ocSSRT). Here we explored how diazepam, which enhances transmission at GABAA receptors, affects ocSSRT. Methods: Nine healthy individuals were randomized to receive placebo, 5 mg or 10 mg doses of diazepam. Each participant received both the dosage of drug and placebo orally on separate days with adequate washout. The ocSSRT and simple reaction time (RT) were estimated through a stop-signal task delivered via a battery-operated box incorporating green (Go) and red (Stop) light-emitting diodes. The task was performed just before and 1 h after dosing. Result: The mean change in ocSSRT after 10 mg diazepam was significantly higher (+27 ms) than for placebo (−1 ms; p = 0.012). By contrast, the mean change in simple response time remained comparable in all three dosing groups (p = 0.419). Conclusion: Our results confirm that a single therapeutic adult dose of diazepam can alter motor inhibition in drug naïve healthy individuals. The selective effect of diazepam on ocSSRT but not simple RT suggests that GABAergic neurons may play a critical role in movement-stopping.
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Affiliation(s)
- Swagata Sarkar
- Department of Neurology, Institute of Neurosciences Kolkata, Kolkata, India.,Department of Physiology, University of Calcutta, Kolkata, India
| | - Supriyo Choudhury
- Department of Neurology, Institute of Neurosciences Kolkata, Kolkata, India
| | - Nazrul Islam
- Department of Neurology, National Institute of Neurosciences and Hospital, Dhaka, Bangladesh
| | | | | | - Mark R Baker
- Department of Neurology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.,Department of Clinical Neurophysiology, Royal Victoria Infirmary, Newcastle upon Tyne, United Kingdom.,The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Stuart N Baker
- The Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Hrishikesh Kumar
- Department of Neurology, Institute of Neurosciences Kolkata, Kolkata, India
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11
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Andrashko V, Novak T, Brunovsky M, Klirova M, Sos P, Horacek J. The Antidepressant Effect of Ketamine Is Dampened by Concomitant Benzodiazepine Medication. Front Psychiatry 2020; 11:844. [PMID: 33005153 PMCID: PMC7485124 DOI: 10.3389/fpsyt.2020.00844] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Accepted: 08/03/2020] [Indexed: 11/29/2022] Open
Abstract
The rapid antidepressant effect of ketamine has become a breakthrough in the research and treatment of depression. Although predictive and modulating factors of the response to ketamine are broadly studied, little is known about optimal concurrent medication protocols. Concerning gamma-aminobutyric acid neurotransmission being a shared target for both ketamine and benzodiazepines (BZD), we evaluated the influence of BZD on the antidepressant effect of a single ketamine infusion in depressed patients. Data from 47 patients (27 females) with major depression (MADRS ≥ 20, ≥ 1 prior nonresponse to antidepressant treatment in current episode) who participated in two previous studies (EudraCT Number: 2009-010625-39 and 2013-000952-17) entered the analysis. All of the subjects were given an infusion of a subanesthetic dose of racemic ketamine (0.54 mg per kg) as an add-on medication to ongoing antidepressant treatment. Thirteen patients (28%) reached ≥ 50% reduction in MADRS within one week after ketamine administration. Nineteen (40%) patients took concomitant benzodiazepines on a daily basis. The doses of BZDs were significantly higher in nonresponders (p=0.007). ROC analysis distinguished responders from nonresponders by a criterion of >8mg of diazepam equivalent dose (DZ equivalent) with a sensitivity of 80% and a specificity of 85% (p<0.001). RM-ANOVA revealed a different time pattern of response to ketamine between the BZD+ (>8mg of DZ equivalent) and BZD- (≤8mg of DZ equivalent) groups, with a significantly worse outcome in BZD+ on day 3 (p=0.04) and day 7 (p=0.02). The results of the study indicate that concomitant benzodiazepine treatment in higher doses may attenuate ketamine's antidepressant effect. The pathophysiological, clinical and methodological implications of this finding should be considered in future research and ketamine treatment.
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Affiliation(s)
- Veronika Andrashko
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia.,Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Tomas Novak
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia.,Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Martin Brunovsky
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia.,Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Monika Klirova
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia.,Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Peter Sos
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia
| | - Jiri Horacek
- Clinical Research of Mental Disorders, National Institute of Mental Health, Klecany, Czechia.,Third Faculty of Medicine, Charles University, Prague, Czechia
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12
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Terejko K, Kaczor PT, Michałowski MA, Dąbrowska A, Mozrzymas JW. The C loop at the orthosteric binding site is critically involved in GABA A receptor gating. Neuropharmacology 2019; 166:107903. [PMID: 31972511 DOI: 10.1016/j.neuropharm.2019.107903] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 11/15/2019] [Accepted: 12/02/2019] [Indexed: 02/02/2023]
Abstract
GABAA receptors (GABAARs) play a crucial role in mammalian adult brain inhibition. The dysfunction of GABAergic drive is related to such disorders as epilepsy, schizophrenia, and depression. Substantial progress has recently been made in describing the static structure of GABAARs, but the molecular mechanisms that underlie the activation process remain elusive. The C loop of the GABAAR structure shows the largest movement upon ligand binding to the orthosteric binding site, a phenomenon that is referred to as "capping." The C loop is known to be involved in agonist binding, but its role in the gating of Cys-loop receptors is still debated. Herein, we investigated this issue by analyzing the impact of a β2F200 residue mutation of the C loop on gating properties of α1β2γ2 GABAARs. Extensive analyses and the modeling of current responses to saturating agonist application demonstrated that this mutation strongly affected preactivation, opening, closing and desensitization, i.e. all considered gating steps. Single-channel analysis revealed that the β2F200 mutation slowed all shut time components, and open times were shortened. Model fitting of these single-channel data further confirmed that the β2F200 mutation strongly affected all of the gating characteristics. We also found that this mutation altered receptor sensitivity to the benzodiazepine flurazepam, which was attributable to a change in preactivation kinetics. In silico analysis indicated that the β2F200 mutation resulted in distortion of the C loop structure, causing the movement of its tip from the binding site. Altogether, we provide the first evidence that C loop critically controls GABAAR gating.
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Affiliation(s)
- Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland.
| | - Przemysław T Kaczor
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland
| | - Agnieszka Dąbrowska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland
| | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, ul. Chałubińskiego 3A, 50-368, Wrocław, Poland; Department of Molecular Physiology and Neurobiology, University of Wrocław, ul. Sienkiewicza 21, 50-335, Wrocław, Poland.
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13
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Abstract
Insomnia poses significant challenges to public health. It is a common condition associated with marked impairment in function and quality of life, psychiatric and physical morbidity, and accidents. As such, it is important that effective treatment is provided in clinical practice. To this end, this paper reviews critical aspects of the assessment of insomnia and the available treatment options. These options include both non-medication treatments, most notably cognitive behavioral therapy for insomnia, and a variety of pharmacologic therapies such as benzodiazepines, "z-drugs", melatonin receptor agonists, selective histamine H1 antagonists, orexin antagonists, antidepressants, antipsychotics, anticonvulsants, and non-selective antihistamines. A review of the available research indicates that rigorous double-blind, randomized, controlled trials are lacking for some of the most commonly administered insomnia therapies. However, there are an array of interventions which have been demonstrated to have therapeutic effects in insomnia in trials with the above features, and whose risk/benefit profiles have been well characterized. These interventions can form the basis for systematic, evidence-based treatment of insomnia in clinical practice. We review this evidence base and highlight areas where more studies are needed, with the aim of providing a resource for improving the clinical management of the many patients with insomnia.
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Affiliation(s)
- Andrew D. Krystal
- Department of PsychiatryUniversity of California San Francisco School of MedicineSan FranciscoCAUSA,Department of NeurologyUniversity of California San Francisco School of MedicineSan FranciscoCAUSA
| | - Aric A. Prather
- Department of PsychiatryUniversity of California San Francisco School of MedicineSan FranciscoCAUSA
| | - Liza H. Ashbrook
- Department of NeurologyUniversity of California San Francisco School of MedicineSan FranciscoCAUSA
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14
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Influence of midazolam premedication on intraoperative EEG signatures in elderly patients. Clin Neurophysiol 2019; 130:1673-1681. [PMID: 31351371 DOI: 10.1016/j.clinph.2019.05.035] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 04/23/2019] [Accepted: 05/30/2019] [Indexed: 12/25/2022]
Abstract
OBJECTIVE To investigate the influence of midazolam premedication on the EEG-spectrum before and during general anesthesia in elderly patients. METHODS Patients aged ≥65 years, undergoing elective surgery were included in this prospective observational study. A continuous pre- and intraoperative frontal EEG was recorded in patients who received premedication with midazolam (Mid, n = 15) and patients who did not (noMid, n = 30). Absolute power within the delta (0.5-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (12-25 Hz) frequency-bands was analyzed in EEG-sections before (pre-induction), and after induction of anesthesia with propofol (post-induction), as well as during general anesthesia with either propofol or volatile-anesthetics (intra-operative). RESULTS Pre-induction, α-power of Mid patients was lower compared with noMid-patients (α-power: Mid: -10.75 dB vs. noMid: -9.20 dB; p = 0.036). After induction of anesthesia Mid-patients displayed a stronger increase of frontal α-power resulting in higher absolute α-power at post-induction state, (α-power: Mid -3.56 dB vs. noMid: -6.69 dB; p = 0.004), which remained higher intraoperatively (α-power: Mid: -2.12 dB vs. noMid: -6.10 dB; p = 0.024). CONCLUSION Midazolam premedication alters the intraoperative EEG-spectrum in elderly patients. SIGNIFICANCE This finding provides further evidence for the role of GABAergic activation in the induction of elevated, frontal α-power during general anesthesia. TRIAL REGISTRY NUMBER NCT02265263. 23 September 2014. Principal investigator: Prof. Dr. med. Claudia Spies. (https://clinicaltrials.gov/ct2/show/NCT02265263).
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15
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Payghan PV, Nath Roy S, Bhattacharyya D, Ghoshal N. Cross-talk between allosteric and orthosteric binding sites of γ-amino butyric acid type A receptors (GABAA-Rs): A computational study revealing the structural basis of selectivity. J Biomol Struct Dyn 2019; 37:3065-3080. [DOI: 10.1080/07391102.2018.1508367] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Pavan V. Payghan
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | | | - Nanda Ghoshal
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
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16
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Steinbach JH, Akk G. Applying the Monod-Wyman-Changeux Allosteric Activation Model to Pseudo-Steady-State Responses from GABA A Receptors. Mol Pharmacol 2018; 95:106-119. [PMID: 30333132 DOI: 10.1124/mol.118.113787] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/12/2018] [Indexed: 12/16/2022] Open
Abstract
The Monod-Wyman-Changeux (MWC) cyclic model was described as a kinetic scheme to explain enzyme function and modulation more than 50 years ago and was proposed as a model for understanding the activation of transmitter-gated channels soon afterward. More recently, the MWC model has been used to describe the activation of the GABAA receptor by the transmitter, GABA, and drugs that bind to separate sites on the receptor. It is most interesting that the MWC formalism can also describe the interactions among drugs that activate the receptor. In this review, we describe properties of the MWC model that have been explored experimentally using the GABAA receptor, summarize analytical expressions for activation and interaction for drugs, and briefly review experimental results.
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Affiliation(s)
- Joe Henry Steinbach
- Department of Anesthesiology, and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri
| | - Gustav Akk
- Department of Anesthesiology, and Taylor Family Institute for Innovative Psychiatric Research, Washington University School of Medicine, St. Louis, Missouri
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17
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Nicholson MW, Sweeney A, Pekle E, Alam S, Ali AB, Duchen M, Jovanovic JN. Diazepam-induced loss of inhibitory synapses mediated by PLCδ/ Ca 2+/calcineurin signalling downstream of GABAA receptors. Mol Psychiatry 2018; 23:1851-1867. [PMID: 29904150 PMCID: PMC6232101 DOI: 10.1038/s41380-018-0100-y] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2017] [Revised: 04/09/2018] [Accepted: 05/01/2018] [Indexed: 11/29/2022]
Abstract
Benzodiazepines facilitate the inhibitory actions of GABA by binding to γ-aminobutyric acid type A receptors (GABAARs), GABA-gated chloride/bicarbonate channels, which are the key mediators of transmission at inhibitory synapses in the brain. This activity underpins potent anxiolytic, anticonvulsant and hypnotic effects of benzodiazepines in patients. However, extended benzodiazepine treatments lead to development of tolerance, a process which, despite its important therapeutic implications, remains poorly characterised. Here we report that prolonged exposure to diazepam, the most widely used benzodiazepine in clinic, leads to a gradual disruption of neuronal inhibitory GABAergic synapses. The loss of synapses and the preceding, time- and dose-dependent decrease in surface levels of GABAARs, mediated by dynamin-dependent internalisation, were blocked by Ro 15-1788, a competitive benzodiazepine antagonist, and bicuculline, a competitive GABA antagonist, indicating that prolonged enhancement of GABAAR activity by diazepam is integral to the underlying molecular mechanism. Characterisation of this mechanism has revealed a metabotropic-type signalling downstream of GABAARs, involving mobilisation of Ca2+ from the intracellular stores and activation of the Ca2+/calmodulin-dependent phosphatase calcineurin, which, in turn, dephosphorylates GABAARs and promotes their endocytosis, leading to disassembly of inhibitory synapses. Furthermore, functional coupling between GABAARs and Ca2+ stores was sensitive to phospholipase C (PLC) inhibition by U73122, and regulated by PLCδ, a PLC isoform found in direct association with GABAARs. Thus, a PLCδ/Ca2+/calcineurin signalling cascade converts the initial enhancement of GABAARs by benzodiazepines to a long-term downregulation of GABAergic synapses, this potentially underpinning the development of pharmacological and behavioural tolerance to these widely prescribed drugs.
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Affiliation(s)
| | - Aaron Sweeney
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Eva Pekle
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Sabina Alam
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Afia B Ali
- UCL School of Pharmacy, University College London, London, WC1N 1AX, UK
| | - Michael Duchen
- Neuroscience, Physiology and Pharmacology, University College London, WC1E 6BT, London, UK
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18
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Gravielle MC. Regulation of GABAA receptors by prolonged exposure to endogenous and exogenous ligands. Neurochem Int 2018; 118:96-104. [DOI: 10.1016/j.neuint.2018.05.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 05/22/2018] [Accepted: 05/30/2018] [Indexed: 02/08/2023]
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19
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Jatczak-Śliwa M, Terejko K, Brodzki M, Michałowski MA, Czyzewska MM, Nowicka JM, Andrzejczak A, Srinivasan R, Mozrzymas JW. Distinct Modulation of Spontaneous and GABA-Evoked Gating by Flurazepam Shapes Cross-Talk Between Agonist-Free and Liganded GABA A Receptor Activity. Front Cell Neurosci 2018; 12:237. [PMID: 30210295 PMCID: PMC6121034 DOI: 10.3389/fncel.2018.00237] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 07/17/2018] [Indexed: 11/13/2022] Open
Abstract
GABAA receptors (GABAARs) play a crucial inhibitory role in the CNS. Benzodiazepines (BDZs) are positive modulators of specific subtypes of GABAARs, but the underlying mechanism remains obscure. Early studies demonstrated the major impact of BDZs on binding and more recent investigations indicated gating, but it is unclear which transitions are affected. Moreover, the upregulation of GABAAR spontaneous activity by BDZs indicates their impact on receptor gating but the underlying mechanisms remain unknown. Herein, we investigated the effect of a BDZ (flurazepam) on the spontaneous and GABA-induced activity for wild-type (WT, α1β2γ2) and mutated (at the orthosteric binding site α1F64) GABAARs. Surprisingly, in spite of the localization at the binding site, these mutations increased the spontaneous activity. Flurazepam (FLU) upregulated this activity for mutants and WT receptors to a similar extent by affecting opening/closing transitions. Spontaneous activity affected GABA-evoked currents and is manifested as an overshoot after agonist removal that depended on the modulation by BDZs. We explain the mechanism of this phenomenon as a cross-desensitization of ligand-activated and spontaneously active receptors. Moreover, due to spontaneous activity, FLU-pretreatment and co-application (agonist + FLU) protocols yielded distinct results. We provide also the first evidence that GABAAR may enter the desensitized state in the absence of GABA in a FLU-dependent manner. Based on our data and model simulations, we propose that FLU affects agonist-induced gating by modifying primarily preactivation and desensitization. We conclude that the mechanisms of modulation of spontaneous and ligand-activated GABAAR activity concerns gating but distinct transitions are affected in spontaneous and agonist-evoked activity.
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Affiliation(s)
- Magdalena Jatczak-Śliwa
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Katarzyna Terejko
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Marek Brodzki
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Michał A Michałowski
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland.,Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | - Marta M Czyzewska
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Joanna M Nowicka
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
| | - Anna Andrzejczak
- Department of Molecular Physiology and Neurobiology, University of Wrocław, Wrocław, Poland
| | | | - Jerzy W Mozrzymas
- Laboratory of Neuroscience, Department of Biophysics, Wrocław Medical University, Wrocław, Poland
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20
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Gielen M, Corringer P. The dual-gate model for pentameric ligand-gated ion channels activation and desensitization. J Physiol 2018; 596:1873-1902. [PMID: 29484660 PMCID: PMC5978336 DOI: 10.1113/jp275100] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 01/17/2018] [Accepted: 01/17/2018] [Indexed: 12/15/2022] Open
Abstract
Pentameric ligand-gated ion channels (pLGICs) mediate fast neurotransmission in the nervous system. Their dysfunction is associated with psychiatric, neurological and neurodegenerative disorders such as schizophrenia, epilepsy and Alzheimer's disease. Understanding their biophysical and pharmacological properties, at both the functional and the structural level, thus holds many therapeutic promises. In addition to their agonist-elicited activation, most pLGICs display another key allosteric property, namely desensitization, in which they enter a shut state refractory to activation upon sustained agonist binding. While the activation mechanisms of several pLGICs have been revealed at near-atomic resolution, the structural foundation of desensitization has long remained elusive. Recent structural and functional data now suggest that the activation and desensitization gates are distinct, and are located at both sides of the ion channel. Such a 'dual gate mechanism' accounts for the marked allosteric effects of channel blockers, a feature illustrated herein by theoretical kinetics simulations. Comparison with other classes of ligand- and voltage-gated ion channels shows that this dual gate mechanism emerges as a common theme for the desensitization and inactivation properties of structurally unrelated ion channels.
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Affiliation(s)
- Marc Gielen
- Channel Receptors UnitInstitut PasteurCNRS UMR 3571ParisFrance
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21
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Pflanz NC, Daszkowski AW, Cornelison GL, Trudell JR, Mihic SJ. An intersubunit electrostatic interaction in the GABA A receptor facilitates its responses to benzodiazepines. J Biol Chem 2018; 293:8264-8274. [PMID: 29622679 DOI: 10.1074/jbc.ra118.002128] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 04/04/2018] [Indexed: 02/01/2023] Open
Abstract
Benzodiazepines are positive allosteric modulators of the GABAA receptor (GABAAR), acting at the α-γ subunit interface to enhance GABAAR function. GABA or benzodiazepine binding induces distinct conformational changes in the GABAAR. The molecular rearrangements in the GABAAR following benzodiazepine binding remain to be fully elucidated. Using two molecular models of the GABAAR, we identified electrostatic interactions between specific amino acids at the α-γ subunit interface that were broken by, or formed after, benzodiazepine binding. Using two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes, we investigated these interactions by substituting one or both amino acids of each potential pair. We found that Lys104 in the α1 subunit forms an electrostatic bond with Asp75 of the γ2 subunit after benzodiazepine binding and that this bond stabilizes the positively modified state of the receptor. Substitution of these two residues to cysteine and subsequent covalent linkage between them increased the receptor's sensitivity to low GABA concentrations and decreased its response to benzodiazepines, producing a GABAAR that resembles a benzodiazepine-bound WT GABAAR. Breaking this bond restored sensitivity to GABA to WT levels and increased the receptor's response to benzodiazepines. The α1 Lys104 and γ2 Asp75 interaction did not play a role in ethanol or neurosteroid modulation of GABAAR, suggesting that different modulators induce different conformational changes in the receptor. These findings may help explain the additive or synergistic effects of modulators acting at the GABAAR.
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Affiliation(s)
- Natasha C Pflanz
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol and Addiction Research, Institutes for Neuroscience and Cell and Molecular Biology, University of Texas, Austin, Texas 78712
| | - Anna W Daszkowski
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol and Addiction Research, Institutes for Neuroscience and Cell and Molecular Biology, University of Texas, Austin, Texas 78712
| | - Garrett L Cornelison
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol and Addiction Research, Institutes for Neuroscience and Cell and Molecular Biology, University of Texas, Austin, Texas 78712
| | - James R Trudell
- Department of Anesthesia, Stanford University School of Medicine, Stanford, California 94305
| | - S John Mihic
- Department of Neuroscience, Division of Pharmacology and Toxicology, Waggoner Center for Alcohol and Addiction Research, Institutes for Neuroscience and Cell and Molecular Biology, University of Texas, Austin, Texas 78712.
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22
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Clinical Sleep-Wake Disorders II: Focus on Insomnia and Circadian Rhythm Sleep Disorders. Handb Exp Pharmacol 2017; 253:261-276. [PMID: 28707143 DOI: 10.1007/164_2017_40] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Insomnia and circadian rhythm sleep disorders affect large proportions of the population and have pronounced effects on quality of life and daytime performance. While the neurobiology of insomnia is not yet fully understood, circadian rhythm sleep disorders are assumed to be caused by a mismatch between the individual circadian phase position and the desired sleep-wake schedule. Benzodiazepines and non-benzodiazepine positive allosteric GABAA receptor modulators improve sleep onset and maintenance in the short-term treatment of insomnia. However, tolerance and dependence are important side effects. Sedating antidepressants are frequently prescribed for insomnia, however, only few randomised controlled trials have been published so far. Melatonin and melatonin receptor agonists are considered to be an option for the treatment of insomnia especially because of their minimal abuse potential and safety. First data on orexin (aka hypocretin) receptor antagonists are promising, however, the risk-benefit ratio needs to be further evaluated. With respect to circadian rhythm sleep disorders, there is solid evidence from meta-analyses supporting the use of melatonin in jet lag disorder to accelerate entrainment to the new time zone, and in delayed sleep phase disorder to advance sleep-wake rhythms. In addition to that, there is evidence supporting the use of melatonin in patients with shift work disorder in order to promote daytime sleep after night shifts.
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23
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Cardinali DP, Golombek DA, Rosenstein RE, Brusco LI, Vigo DE. Assessing the efficacy of melatonin to curtail benzodiazepine/Z drug abuse. Pharmacol Res 2016; 109:12-23. [DOI: 10.1016/j.phrs.2015.08.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 08/17/2015] [Accepted: 08/19/2015] [Indexed: 12/15/2022]
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24
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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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25
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Goldschen-Ohm MP, Haroldson A, Jones MV, Pearce RA. A nonequilibrium binary elements-based kinetic model for benzodiazepine regulation of GABAA receptors. ACTA ACUST UNITED AC 2015; 144:27-39. [PMID: 24981228 PMCID: PMC4076519 DOI: 10.1085/jgp.201411183] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A nonequilibrium kinetic model that explicitly treats the energetics of interactions between structural domains is used to describe positive modulation of the GABAA receptor by benzodiazepines. Ion channels, like many other proteins, are composed of multiple structural domains. A stimulus that impinges on one domain, such as binding of a ligand to its recognition site, can influence the activity of another domain, such as a transmembrane channel gate, through interdomain interactions. Kinetic schemes that describe the function of interacting domains typically incorporate a minimal number of states and transitions, and do not explicitly model interactions between domains. Here, we develop a kinetic model of the GABAA receptor, a ligand-gated ion channel modulated by numerous compounds including benzodiazepines, a class of drugs used clinically as sedatives and anxiolytics. Our model explicitly treats both the kinetics of distinct functional domains within the receptor and the interactions between these domains. The model describes not only how benzodiazepines that potentiate GABAA receptor activity, such as diazepam, affect peak current dose–response relationships in the presence of desensitization, but also their effect on the detailed kinetics of current activation, desensitization, and deactivation in response to various stimulation protocols. Finally, our model explains positive modulation by benzodiazepines of receptor currents elicited by either full or partial agonists, and can resolve conflicting observations arguing for benzodiazepine modulation of agonist binding versus channel gating.
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Affiliation(s)
- Marcel P Goldschen-Ohm
- Department of Neuroscience and Department of Anesthesiology, University of Wisconsin, Madison, WI 53706
| | - Alexander Haroldson
- Department of Neuroscience and Department of Anesthesiology, University of Wisconsin, Madison, WI 53706
| | - Mathew V Jones
- Department of Neuroscience and Department of Anesthesiology, University of Wisconsin, Madison, WI 53706
| | - Robert A Pearce
- Department of Neuroscience and Department of Anesthesiology, University of Wisconsin, Madison, WI 53706
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26
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Morin CM, Drake CL, Harvey AG, Krystal AD, Manber R, Riemann D, Spiegelhalder K. Insomnia disorder. Nat Rev Dis Primers 2015; 1:15026. [PMID: 27189779 DOI: 10.1038/nrdp.2015.26] [Citation(s) in RCA: 337] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Insomnia disorder affects a large proportion of the population on a situational, recurrent or chronic basis and is among the most common complaints in medical practice. The disorder is predominantly characterized by dissatisfaction with sleep duration or quality and difficulties initiating or maintaining sleep, along with substantial distress and impairments of daytime functioning. It can present as the chief complaint or, more often, co-occurs with other medical or psychiatric disorders, such as pain and depression. Persistent insomnia has been linked with adverse long-term health outcomes, including diminished quality of life and physical and psychological morbidity. Despite its high prevalence and burden, the aetiology and pathophysiology of insomnia is poorly understood. In the past decade, important changes in classification and diagnostic paradigms have instigated a move from a purely symptom-based conceptualization to the recognition of insomnia as a disorder in its own right. These changes have been paralleled by key advances in therapy, with generic pharmacological and psychological interventions being increasingly replaced by approaches that have sleep-specific and insomnia-specific therapeutic targets. Psychological and pharmacological therapies effectively reduce the time it takes to fall asleep and the time spent awake after sleep onset, and produce a modest increase in total sleep time; these are outcomes that correlate with improvements in daytime functioning. Despite this progress, several challenges remain, including the need to improve our knowledge of the mechanisms that underlie insomnia and to develop more cost-effective, efficient and accessible therapies.
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Affiliation(s)
- Charles M Morin
- Université Laval, École de psychologie, 2325 rue des Bibliothèques, Québec City, Québec G1V 0A6, Canada
| | - Christopher L Drake
- Henry Ford Hospital Sleep Disorders and Research Center, Detroit, Michigan, USA
| | - Allison G Harvey
- Department of Psychology, University of California, Berkeley, Berkeley, California, USA
| | - Andrew D Krystal
- Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine, Durham, North Carolina, USA
| | - Rachel Manber
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, California, USA
| | - Dieter Riemann
- Department of Clinical Psychology and Psychophysiology/Sleep Medicine, Center for Mental Disorders, University of Freiburg Medical Center, Freiburg, Germany
| | - Kai Spiegelhalder
- Department of Clinical Psychology and Psychophysiology/Sleep Medicine, Center for Mental Disorders, University of Freiburg Medical Center, Freiburg, Germany
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27
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Weltzin MM, Schulte MK. Desformylflustrabromine Modulates α4β2 Neuronal Nicotinic Acetylcholine Receptor High- and Low-Sensitivity Isoforms at Allosteric Clefts Containing the β2 Subunit. J Pharmacol Exp Ther 2015; 354:184-94. [PMID: 26025967 DOI: 10.1124/jpet.115.223933] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 05/22/2015] [Indexed: 12/13/2022] Open
Abstract
Alterations in expression patterns of α4β2 nicotinic acetylcholine receptors have been demonstrated to alter cholinergic neurotransmission and are implicated in neurologic disorders, including autism, nicotine addiction, Alzheimer's disease, and Parkinson's disease. Positive allosteric modulators (PAMs) represent promising new leads in the development of therapeutic agents for the treatment of these disorders. This study investigates the involvement of the β2-containing subunit interfaces of α4β2 receptors in the modulation of acetylcholine (ACh)-induced responses by the PAM desformylflustrabromine (dFBr). Eight amino acids on the principal face of the β2 subunit were mutated to alanine to explore the involvement of this region in the potentiation of ACh-induced currents by dFBr. ACh-induced responses obtained from wild-type and mutant α4β2 receptors expressed in Xenopus laevis oocytes were recorded in the presence and absence of dFBr using two-electrode voltage clamp electrophysiology. Wild-type and mutant receptors were expressed in both high and low ACh sensitivity isoforms by using biased injection ratios of 1:5 or 5:1 α4 to β2 complementary RNA. Mutations were made in the B, C, and A loops of the principal face of the β2 subunit, which are regions not involved in the binding of ACh. Mutant β2(Y120A) significantly eliminated dFBr potency in both isoform preparations. Several other mutations altered dFBr potentiation levels in both preparations. Our findings support the involvement of the principal face of the β2 subunit in dFBr modulation of ACh-induced responses. Findings from this study will aid in the improved design of dFBr-like PAMs for potential therapeutic use.
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Affiliation(s)
- Maegan M Weltzin
- Division of Neurobiology, Barrow Neurologic Institute, Phoenix, Arizona (M.M.W.); and Department of Pharmaceutical Science, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, Pennsylvania (M.K.S.)
| | - Marvin K Schulte
- Division of Neurobiology, Barrow Neurologic Institute, Phoenix, Arizona (M.M.W.); and Department of Pharmaceutical Science, Philadelphia College of Pharmacy, University of the Sciences, Philadelphia, Pennsylvania (M.K.S.)
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Christopoulos A, Changeux JP, Catterall WA, Fabbro D, Burris TP, Cidlowski JA, Olsen RW, Peters JA, Neubig RR, Pin JP, Sexton PM, Kenakin TP, Ehlert FJ, Spedding M, Langmead CJ. International Union of Basic and Clinical Pharmacology. XC. multisite pharmacology: recommendations for the nomenclature of receptor allosterism and allosteric ligands. Pharmacol Rev 2014; 66:918-47. [PMID: 25026896 PMCID: PMC11060431 DOI: 10.1124/pr.114.008862] [Citation(s) in RCA: 151] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Allosteric interactions play vital roles in metabolic processes and signal transduction and, more recently, have become the focus of numerous pharmacological studies because of the potential for discovering more target-selective chemical probes and therapeutic agents. In addition to classic early studies on enzymes, there are now examples of small molecule allosteric modulators for all superfamilies of receptors encoded by the genome, including ligand- and voltage-gated ion channels, G protein-coupled receptors, nuclear hormone receptors, and receptor tyrosine kinases. As a consequence, a vast array of pharmacologic behaviors has been ascribed to allosteric ligands that can vary in a target-, ligand-, and cell-/tissue-dependent manner. The current article presents an overview of allostery as applied to receptor families and approaches for detecting and validating allosteric interactions and gives recommendations for the nomenclature of allosteric ligands and their properties.
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Affiliation(s)
- Arthur Christopoulos
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Jean-Pierre Changeux
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - William A Catterall
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Doriano Fabbro
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Thomas P Burris
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - John A Cidlowski
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Richard W Olsen
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - John A Peters
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Richard R Neubig
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Jean-Philippe Pin
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Patrick M Sexton
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Terry P Kenakin
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Frederick J Ehlert
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Michael Spedding
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
| | - Christopher J Langmead
- Drug Discovery Biology and Department of Pharmacology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia (A.C., P.M.S., C.J.L.); Collège de France and CNRS URA 2182, Institut Pasteur, Paris, France (J.-P.C.); Department of Pharmacology, School of Medicine, University of Washington, Seattle, Washington (W.A.C.); PIQUR Therapeutics AG, Basel, Switzerland (D.F.); Department of Pharmacological & Physiological Science, Saint Louis University School of Medicine, St. Louis, Louisiana (T.P.B.); Signal Transduction Laboratory, Molecular Endocrinology Group, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina (J.A.C.); Department of Molecular and Medical Pharmacology, University of California, Los Angeles, California (R.W.O.); Division of Neuroscience, School of Medicine, University of Dundee, Scotland, United Kingdom (J.A.P.); Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (R.R.N.); Institut de Genomique Fonctionelle, CNRS, Montpellier, France (J.-P.P.); Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina (T.P.K.); Department of Pharmacology, University of California, Irvine, California (F.J.E.); and Research Solutions SARL, Paris, France (M.S.)
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What ligand-gated ion channels can tell us about the allosteric regulation of G protein-coupled receptors. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2014; 115:291-347. [PMID: 23415097 DOI: 10.1016/b978-0-12-394587-7.00007-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
The GABA(A) receptor is the target for a number of important allosteric drugs used in medicine, including benzodiazepines and anesthetics. These modulators have variable effects on the potency and maximal response of macroscopic currents elicited by different GABA(A) receptor agonists, yet this modulation is consistent with a two-state model in which the allosteric ligand has invariant affinity constants for the active and inactive states. Analysis of the effects of an allosteric agonist, like etomidate, on the population current provides a means of estimating the gating constant of the unliganded GABA(A) receptor (∼10(-4)). In contrast, allosteric interactions at the M(2) muscarinic receptor are often inconsistent with a two-state model. Analyzing allosterism within the constraints of a two-state model, nonetheless, provides an unbiased measure of probe dependence as well as clues to the mechanism of allosteric modulation. The rather simple allosteric effect of affinity-only modulation is difficult to explain and suggests modulation of a peripheral orthosteric ligand-docking site on the M(2) muscarinic receptor.
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Popescu G, Negrei C, Bălălău D, Ciobanu AM, Baconi D, Bălălău C. Use of benzodiazepines and detoxification with methadone. J Med Life 2014; 7 Spec No. 3:133-6. [PMID: 25870711 PMCID: PMC4391402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
RATIONALE Benzodiazepines are used as anti anxiety drugs, as well as in adjunct treatment for a range of neurological and psychiatric disorders. Abusive patterns of use were increasingly reported and building evidence points to prevalence of benzodiazepines abuse, on one hand as well as to their common abuse in combination with other drugs such as opioids, most frequently. OBJECTIVE The main objective of this research is to conduct a systematic study on the behavior profile of a patient admitted to a prison hospital, who is a benzodiazepines user consecutive to admission into a methadone administration program. METHODS AND RESULTS Statistic values have been taken into account describing the distribution and the distribution form of the various variables studied to find the normality degree of distributions, regarding three measurements at the three moments: before the administration of methadone, immediately after its completion and two months after completion. CONCLUSIONS AND DISCUSSIONS The statistic results obtained speak of a strong positive correlation, allowing the support of the fact that persons diagnosed with prescribed/ unprescribed benzodiazepine, use the display association with the admission into a methadone administration program, based on the assumption which concerns a significant positive association between the use of reported benzodiazepine and the administration of methadone in the questioned patients on admission. As far as the second premise regarding the administration of methadone is concerned it brings about an improvement in the level of benzodiazepines used in research patients, which one may assert that, according to the results obtained, the initiation of methadone therapy in the detoxification program is conducive to the reduction of benzodiazepines use.
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Affiliation(s)
- G Popescu
- Department of Toxicology, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest,
| | - C Negrei
- Department of Toxicology, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest,
| | - D Bălălău
- Department of Toxicology, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest,
| | - AM Ciobanu
- Department of Drug Control, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest,
| | - D Baconi
- Department of Toxicology, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest,
| | - C Bălălău
- Department of Toxicology, “Carol Davila” University of Medicine and Pharmacy, Faculty of Pharmacy, Bucharest, ,“Sf. Pantelimon” Emergency Hospital, Surgical Clinic, “Carol Davila” University of Medicine and Pharmacy, Faculty of General Medicine
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The benzodiazepine diazepam potentiates responses of α1β2γ2L γ-aminobutyric acid type A receptors activated by either γ-aminobutyric acid or allosteric agonists. Anesthesiology 2013; 118:1417-25. [PMID: 23407108 DOI: 10.1097/aln.0b013e318289bcd3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The γ-aminobutyric acid (GABA) type A receptor is a target for several anesthetics, anticonvulsants, anxiolytics, and sedatives. Neurosteroids, barbiturates, and etomidate both potentiate responses to GABA and allosterically activate the receptor. We examined the ability of a benzodiazepine, diazepam, to potentiate responses to allosteric agonists. METHODS The GABA type A receptors were expressed in human embryonic kidney 293 cells and studied using whole-cell and single-channel patch clamp. The receptors were activated by the orthosteric agonist GABA and allosteric agonists pentobarbital, etomidate, and alfaxalone. RESULTS Diazepam is equally potent at enhancing responses to orthosteric and allosteric agonists. Diazepam EC50s were 25 ± 4, 26 ± 6, 33 ± 6, and 26 ± 3 nm for receptors activated by GABA, pentobarbital, etomidate, and alfaxalone, respectively (mean ± SD, 5-6 cells at each condition). Mutations to the benzodiazepine-binding site (α1(H101C), γ2(R144C), γ2(R197C)) reduced or removed potentiation for all agonists, and an inverse agonist at the benzodiazepine site reduced responses to all agonists. Single-channel data elicited by GABA demonstrate that in the presence of 1 μm diazepam the prevalence of the longest open-time component is increased from 13 ± 7 (mean ± SD, n = 5 patches) to 27 ± 8% (n = 3 patches) and the rate of channel closing is decreased from 129 ± 28 s(-1) to 47 ± 6 s(-1) (mean ± SD) CONCLUSIONS: We conclude that benzodiazepines do not act by enhancing affinity of the orthosteric site for GABA but rather by increasing channel gating efficacy. The results also demonstrate the presence of interactions between allosteric activators and potentiators, raising a possibility of effects on dosage requirements or changes in side effects.
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Kletke O, Gisselmann G, May A, Hatt H, A. Sergeeva O. Partial agonism of taurine at gamma-containing native and recombinant GABAA receptors. PLoS One 2013; 8:e61733. [PMID: 23637894 PMCID: PMC3640040 DOI: 10.1371/journal.pone.0061733] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 03/13/2013] [Indexed: 11/18/2022] Open
Abstract
Taurine is a semi-essential sulfonic acid found at high concentrations in plasma and mammalian tissues which regulates osmolarity, ion channel activity and glucose homeostasis. The structural requirements of GABAA-receptors (GABAAR) gated by taurine are not yet known. We determined taurine potency and efficacy relative to GABA at different types of recombinant GABAAR occurring in central histaminergic neurons of the mouse hypothalamic tuberomamillary nucleus (TMN) which controls arousal. At binary α1/2β1/3 receptors taurine was as efficient as GABA, whereas incorporation of the γ1/2 subunit reduced taurine efficacy to 60–90% of GABA. The mutation γ2F77I, which abolishes zolpidem potentiation, significantly reduced taurine efficacy at recombinant and native receptors compared to the wild type controls. As taurine was a full- or super- agonist at recombinant αxβ1δ-GABAAR, we generated a chimeric γ2 subunit carrying the δ subunit motif around F77 (MTVFLH). At α1/2β1γ2(MTVFLH) receptors taurine became a super-agonist, similar to δ-containing ternary receptors, but remained a partial agonist at β3-containing receptors. In conclusion, using site-directed mutagenesis we found structural determinants of taurine’s partial agonism at γ-containing GABAA receptors. Our study sheds new light on the β1 subunit conferring the widest range of taurine-efficacies modifying GABAAR function under (patho)physiological conditions.
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Affiliation(s)
- Olaf Kletke
- Department of Cell Physiology of the Ruhr-University, Bochum, Germany
- Department of Neurophysiology, Medical Faculty of Heinrich-Heine University, Düsseldorf, Germany
| | | | - Andrea May
- Department of Neurophysiology, Medical Faculty of Heinrich-Heine University, Düsseldorf, Germany
| | - Hanns Hatt
- Department of Cell Physiology of the Ruhr-University, Bochum, Germany
| | - Olga A. Sergeeva
- Department of Neurophysiology, Medical Faculty of Heinrich-Heine University, Düsseldorf, Germany
- * E-mail:
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Hoffmann K, Xifró RA, Hartweg JL, Spitzlei P, Meis K, Molderings GJ, von Kügelgen I. Inhibitory effects of benzodiazepines on the adenosine A(2B) receptor mediated secretion of interleukin-8 in human mast cells. Eur J Pharmacol 2012; 700:152-8. [PMID: 23266380 DOI: 10.1016/j.ejphar.2012.12.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 11/29/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
The activation of adenosine A(2B) receptors in human mast cells causes pro-inflammatory responses such as the secretion of interleukin-8. There is evidence for an inhibitory effect of benzodiazepines on mast cell mediated symptoms in patients with systemic mast cell activation disease. Therefore, we investigated the effects of benzodiazepines on adenosine A(2B) receptor mediated interleukin-8 production in human mast cell leukaemia (HMC1) cells by an enzyme linked immunosorbent assay. The adenosine analogue N-ethylcarboxamidoadenosine (NECA, 0.3-3 μM) increased interleukin-8 production about 5-fold above baseline. This effect was attenuated by the adenosine A(2B) receptor antagonist MRS1754 (N-(4-cyanophenyl)-2-{4-(2,3,6,7-tetrahydro-2,6-dioxo-1,3-dipropyl-1H-purin-8-yl)phenoxy}-acetamide) 1 μM. In addition, diazepam, 4'-chlorodiazepam and flunitrazepam (1-30 μM) markedly reduced NECA-induced interleukin-8 production in that order of potency, whereas clonazepam showed only a modest inhibition. The inhibitory effect of diazepam was not altered by flumazenil 10 μM or PK11195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide) 10 μM. Diazepam attenuated the NECA-induced expression of mRNA encoding for interleukin-8. Moreover, diazepam and flunitrazepam reduced the increasing effects of NECA on cAMP-response element- and nuclear factor of activated t-cells-driven luciferase reporter gene activities in HMC1 cells. Neither diazepam nor flunitrazepam affected NECA-induced increases in cellular cAMP levels in CHO Flp-In cells stably expressing recombinant human adenosine A(2B) receptors, excluding a direct action of benzodiazepines on human adenosine A(2B) receptors. In conclusion, this is the first study showing an inhibitory action of benzodiazepines on adenosine A(2B) receptor mediated interleukin-8 production in human mast (HMC1) cells. The rank order of potency indicates the involvement of an atypical benzodiazepine binding site.
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Affiliation(s)
- Kristina Hoffmann
- Pharma Center Bonn, Department of Pharmacology and Toxicology, Biomedical Research Center, University of Bonn, Sigmund-Freud-Strasse 25, 53127 Bonn, Germany
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Benzodiazepines modulate GABAA receptors by regulating the preactivation step after GABA binding. J Neurosci 2012; 32:5707-15. [PMID: 22539833 DOI: 10.1523/jneurosci.5663-11.2012] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
GABA(A) receptors (GABA(A)Rs) composed of αβγ subunits are allosterically modulated by the benzodiazepines (BDZs). Agonists at the BDZ binding site potentiate submaximal GABA responses by increasing the apparent affinity of GABA(A)Rs for GABA. Although BDZs were initially thought to affect the binding of GABA agonists, recent studies suggest an effect on receptor gating; however, the involvement of preactivation steps in the modulation by BDZs has not been considered. Consequently, we examined whether BDZ agonists could exert their modulatory effect by displacing the equilibrium between resting and preactivated states of recombinant α1β2γ2 GABA(A)Rs expressed in Xenopus oocytes. For GABA and the partial agonists 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol and piperidine-4-sulfonic acid, we examined BDZ modulation using a simple three-step model incorporating agonist binding, receptor preactivation, and channel opening. The model accounted for diazepam modulation simply by increasing the preactivation constant by approximately fourfold. To assess whether BDZs preferentially affected a specific GABA binding site, pentameric concatamers were used. This demonstrated that single GABA-binding site mutant receptors were equally sensitive to modulation by BDZs compared with wild-type counterparts. Overall, our results suggest that BDZs affect the preactivation step to cause a global conformational rearrangement of GABA(A)Rs, thereby modulating receptor function.
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Venkatachalan SP, Czajkowski C. Structural link between γ-aminobutyric acid type A (GABAA) receptor agonist binding site and inner β-sheet governs channel activation and allosteric drug modulation. J Biol Chem 2012; 287:6714-24. [PMID: 22219195 DOI: 10.1074/jbc.m111.316836] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Rapid opening and closing of pentameric ligand-gated ion channels (pLGICs) regulate information flow throughout the brain. For pLGICs, it is postulated that neurotransmitter-induced movements in the extracellular inner β-sheet trigger channel activation. Homology modeling reveals that the β4-β5 linker physically connects the neurotransmitter binding site to the inner β-sheet. Inserting 1, 2, 4, and 8 glycines in this region of the GABA(A) receptor β-subunit progressively decreases GABA activation and converts the competitive antagonist SR-95531 into a partial agonist, demonstrating that this linker is a key element whose length and flexibility are optimized for efficient signal propagation. Insertions in the α- and γ-subunits have little effect on GABA or SR-95531 actions, suggesting that asymmetric motions in the extracellular domain power pLGIC gating. The effects of insertions on allosteric modulator actions, pentobarbital, and benzodiazepines, have different subunit dependences, indicating that modulator-induced signaling is distinct from agonist gating.
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Barberis A, Petrini EM, Mozrzymas JW. Impact of synaptic neurotransmitter concentration time course on the kinetics and pharmacological modulation of inhibitory synaptic currents. Front Cell Neurosci 2011; 5:6. [PMID: 21734864 PMCID: PMC3123770 DOI: 10.3389/fncel.2011.00006] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 06/05/2011] [Indexed: 12/26/2022] Open
Abstract
The time course of synaptic currents is a crucial determinant of rapid signaling between neurons. Traditionally, the mechanisms underlying the shape of synaptic signals are classified as pre- and post-synaptic. Over the last two decades, an extensive body of evidence indicated that synaptic signals are critically shaped by the neurotransmitter time course which encompasses several phenomena including pre- and post-synaptic ones. The agonist transient depends on neurotransmitter release mechanisms, diffusion within the synaptic cleft, spill-over to the extra-synaptic space, uptake, and binding to post-synaptic receptors. Most estimates indicate that the neurotransmitter transient is very brief, lasting between one hundred up to several hundreds of microseconds, implying that post-synaptic activation is characterized by a high degree of non-equilibrium. Moreover, pharmacological studies provide evidence that the kinetics of agonist transient plays a crucial role in setting the susceptibility of synaptic currents to modulation by a variety of compounds of physiological or clinical relevance. More recently, the role of the neurotransmitter time course has been emphasized by studies carried out on brain slice models that revealed a striking, cell-dependent variability of synaptic agonist waveforms ranging from rapid pulses to slow volume transmission. In the present paper we review the advances on studies addressing the impact of synaptic neurotransmitter transient on kinetics and pharmacological modulation of synaptic currents at inhibitory synapses.
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Affiliation(s)
- Andrea Barberis
- Department of Neuroscience and Brain Technologies, The Italian Institute of Technology Genova, Italy
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37
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Bianchi MT. Context dependent benzodiazepine modulation of GABA(A) receptor opening frequency. Curr Neuropharmacol 2011; 8:10-7. [PMID: 20808542 PMCID: PMC2866457 DOI: 10.2174/157015910790909467] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 11/04/2009] [Accepted: 11/05/2009] [Indexed: 02/04/2023] Open
Abstract
The anxiolytic, hypnotic, and anti-convulsant properties of benzodiazepines (BDZs) require modulation of distinct GABAA receptor α-subtypes. BDZ modulation of GABAA receptors is often described in terms of increased opening frequency, and contrasted with the increased open durations occurring with barbiturate modulation. Several studies spanning single channel, rapid kinetic, and whole cell techniques have suggested that BDZs effect this observed change in frequency through increased affinity for GABA. BDZ-sensitive αβγ isoforms exist at extrasynaptic as well as synaptic locations, where they encounter markedly different concentration and time-course of GABA exposure. Interestingly, this affinity-based mechanism (specifically, decreasing the GABA unbinding rate) is only predicted to increase opening frequency under conditions that allow the unbinding and rebinding cycles typical of prolonged exposure to low GABA concentrations, which are more likely to occur at extrasynaptic GABAA receptors. In contrast, when rebinding is less likely, such as may occur in certain synaptic conditions, the number, but not the frequency, of channel openings increases in response to BDZ modulation. In conclusion, not only can multiple kinetic mechanisms alter channel opening frequency, but a single mechanism – increased affinity – impacts opening frequency differently under different contexts of GABAA receptor activation.
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Affiliation(s)
- Matt T Bianchi
- Neurology Department, Sleep Division, Massachusetts General Hospital, Wang 720, Boston, MA, 02114, USA.
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Morlock EV, Czajkowski C. Different residues in the GABAA receptor benzodiazepine binding pocket mediate benzodiazepine efficacy and binding. Mol Pharmacol 2011; 80:14-22. [PMID: 21447642 DOI: 10.1124/mol.110.069542] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Benzodiazepines (BZDs) exert their therapeutic actions by binding to the GABA(A) receptor (GABA(A)R) and allosterically modulating GABA-induced chloride currents (I(GABA)). A variety of ligands with divergent structures bind to the BZD site, and the structural mechanisms that couple their binding to potentiation of I(GABA) are not well understood. In this study, we measured the effects of individually mutating 22 residues throughout the BZD binding pocket on the abilities of eszopiclone, zolpidem, and flurazepam to potentiate I(GABA). Wild-type and mutant α(1)β(2)γ(2) GABA(A)Rs were expressed in Xenopus laevis oocytes and analyzed using a two-electrode voltage clamp. GABA EC(50), BZD EC(50), and BZD maximal potentiation were measured. These data, combined with previous radioligand binding data describing the mutations' effects on BZD apparent binding affinities (J Neurosci 28:3490-3499, 2008; J Med Chem 51:7243-7252, 2008), were used to distinguish residues within the BZD pocket that contribute to BZD efficacy and BZD binding. We identified six residues whose mutation altered BZD maximal potentiation of I(GABA) (BZD efficacy) without altering BZD binding apparent affinity, three residues whose mutation altered binding but had no effect on BZD efficacy, and four residues whose mutation affected both binding and efficacy. Moreover, depending on the BZD ligand, the effects of some mutations were different, indicating that the structural mechanisms underlying the ability of BZD ligands with divergent structures to potentiate I(GABA) are distinct.
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Affiliation(s)
- Elaine V Morlock
- University of Wisconsin at Madison, 601 Science Drive, Madison, WI 53711, USA
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Hanson SM, Czajkowski C. Disulphide trapping of the GABA(A) receptor reveals the importance of the coupling interface in the action of benzodiazepines. Br J Pharmacol 2011; 162:673-87. [PMID: 20942818 PMCID: PMC3041256 DOI: 10.1111/j.1476-5381.2010.01073.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 09/15/2010] [Accepted: 09/23/2010] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND AND SIGNIFICANCE Although the functional effects of benzodiazepines (BZDs) on GABA(A) receptors have been well characterized, the structural mechanism by which these modulators alter activation of the receptor by GABA is still undefined. EXPERIMENTAL APPROACH We used disulphide trapping between engineered cysteines to probe BZD-induced conformational changes within the γ₂ subunit and at the α₁/γ₂ coupling interface (Loops 2, 7 and 9) of α₁β₂γ₂ GABA(A) receptors. KEY RESULTS Crosslinking γ₂ Loop 9 to γ₂β-strand 9 (via γ₂ S195C/F203C and γ₂ S187C/L206C) significantly decreased maximum potentiation by flurazepam, suggesting that modulation of GABA-induced current (I(GABA)) by flurazepam involves movements of γ₂ Loop 9 relative to γ₂β-strand 9. In contrast, tethering γ₂β-strand 9 to the γ₂ pre-M1 region (via γ₂S202C/S230C) significantly enhanced potentiation by both flurazepam and zolpidem, indicating γ₂S202C/S230C trapped the receptor in a more favourable conformation for positive modulation by BZDs. Intersubunit disulphide bonds formed at the α/γ coupling interface between α₁ Loop 2 and γ₂Loop 9 (α₁D56C/γ₂L198C) prevented flurazepam and zolpidem from efficiently modulating I(GABA) . Disulphide trapping α₁ Loop 2 (α₁D56C) to γ₂β-strand 1 (γ₂P64C) decreased maximal I(GABA) as well as flurazepam potentiation. None of the disulphide bonds affected the ability of the negative modulator, 3-carbomethoxy-4-ethyl-6,7-dimethoxy-β-carboline (DMCM), to inhibit I(GABA) . CONCLUSIONS AND IMPLICATIONS Positive modulation of GABA(A) receptors by BZDs requires reorganization of the loops in the α₁/γ₂ coupling interface. BZD-induced movements at the α/γ coupling interface likely synergize with rearrangements induced by GABA binding at the β/α subunit interfaces to enhance channel activation by GABA.
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Affiliation(s)
- Susan M Hanson
- Department of Physiology, University of Wisconsin-Madison, Madison, WI, USA.
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40
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Sancar F, Czajkowski C. Allosteric modulators induce distinct movements at the GABA-binding site interface of the GABA-A receptor. Neuropharmacology 2010; 60:520-8. [PMID: 21093460 DOI: 10.1016/j.neuropharm.2010.11.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 10/14/2010] [Accepted: 11/10/2010] [Indexed: 10/18/2022]
Abstract
Benzodiazepines (BZDs) and barbiturates exert their CNS actions by binding to GABA-A receptors (GABARs). The structural mechanisms by which these drugs allosterically modulate GABAR function, to either enhance or inhibit GABA-gated current, are poorly understood. Here, we used the substituted cysteine accessibility method to examine and compare structural movements in the GABA-binding site interface triggered by a BZD positive (flurazepam), zero (flumazenil) and negative (3-carbomethoxy-4-ethyl-6,7-dimethoxy-β-carboline, DMCM) modulator as well as the barbiturate pentobarbital. Ten residues located throughout the GABA-binding site interface were individually mutated to cysteine. Wild-type and mutant α(1)β(2)γ(2) GABARs were expressed in Xenopus laevis oocytes and functionally characterized using two-electrode voltage clamp. We measured and compared the rates of modification of the introduced cysteines by sulfhydryl-reactive methanethiosulfonate (MTS) reagents in the absence and presence of BZD-site ligands and pentobarbital. Flurazepam and DMCM each accelerated the rate of reaction at α(1)R131C and slowed the rate of reaction at α(1)E122C, whereas flumazenil had no effect indicating that simple occupation of the BZD binding site is not sufficient to cause movements near these positions. Therefore, BZD-induced movements at these residues are likely associated with the ability of the BZD to modulate GABAR function (BZD efficacy). Low, modulating concentrations of pentobarbital accelerated the rate of reaction at α(1)S68C and β(2)P206C, slowed the rate of reaction at α(1)E122C and had no effect at α(1)R131C. These findings indicate that pentobarbital and BZDs induce different movements in the receptor, providing evidence that the structural mechanisms underlying their allosteric modulation of GABAR function are distinct.
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Affiliation(s)
- Feyza Sancar
- Department of Physiology, University of Wisconsin-Madison, 601 Science Drive, Madison, WI 53711, USA
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41
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Goldschen-Ohm MP, Wagner DA, Petrou S, Jones MV. An epilepsy-related region in the GABA(A) receptor mediates long-distance effects on GABA and benzodiazepine binding sites. Mol Pharmacol 2009; 77:35-45. [PMID: 19846749 DOI: 10.1124/mol.109.058289] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The GABA(A) receptor mutation gamma(2)R43Q causes absence epilepsy in humans. Homology modeling suggests that gamma(2)Arg43, gamma(2)Glu178, and beta(2)Arg117 participate in a salt-bridge network linking the gamma(2) and beta(2) subunits. Here we show that several mutations at these locations exert similar long-distance effects on other intersubunit interfaces involved in GABA and benzodiazepine binding. These mutations alter GABA-evoked receptor kinetics by slowing deactivation, enhancing desensitization, or both. Kinetic modeling and nonstationary noise analysis for gamma(2)R43Q reveal that these effects are due to slowed GABA unbinding and slowed recovery from desensitization. Both gamma(2)R43Q and beta(2)R117K also speed diazepam dissociation from the receptor's benzodiazepine binding interface, as assayed by the rate of decay of diazepam-induced potentiation of GABA-evoked currents. These data demonstrate that gamma(2)Arg43 and beta(2)Arg117 similarly regulate the stability of both the GABA and benzodiazepine binding sites at the distant beta/alpha and alpha/gamma intersubunit interfaces, respectively. A simple explanation for these results is that gamma(2)Arg43 and beta(2)Arg117 participate in interactions between the gamma(2) and beta(2) subunits, disruptions of which alter the neighboring intersubunit binding sites in a similar fashion. In addition, gamma(2)Arg43 and gamma(2)Glu178 regulate desensitization, probably mediated within the transmembrane domains near the pore. Therefore, mutations at the gamma/beta intersubunit interface have specific long-distance effects that are propagated widely throughout the GABA(A) receptor protein.
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42
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Berezhnoy D, Gibbs TT, Farb DH. Docking of 1,4-benzodiazepines in the alpha1/gamma2 GABA(A) receptor modulator site. Mol Pharmacol 2009; 76:440-50. [PMID: 19483108 DOI: 10.1124/mol.109.054650] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Positive allosteric modulation of the GABA(A) receptor (GABA(A)R) via the benzodiazepine recognition site is the mechanism whereby diverse chemical classes of therapeutic agents act to reduce anxiety, induce and maintain sleep, reduce seizures, and induce conscious sedation. The binding of such therapeutic agents to this allosteric modulatory site increases the affinity of GABA for the agonist recognition site. A major unanswered question, however, relates to how positive allosteric modulators dock in the 1,4-benzodiazepine (BZD) recognition site. In the present study, the X-ray structure of an acetylcholine binding protein from the snail Lymnea stagnalis and the results from site-directed affinity-labeling studies were used as the basis for modeling of the BZD binding pocket at the alpha(1)/gamma(2) subunit interface. A tethered BZD was introduced into the binding pocket, and molecular simulations were carried out to yield a set of candidate orientations of the BZD ligand in the binding pocket. Candidate orientations were refined based on known structure-activity and stereospecificity characteristics of BZDs and the impact of the alpha(1)H101R mutation. Results favor a model in which the BZD molecule is oriented such that the C5-phenyl substituent extends approximately parallel to the plane of the membrane rather than parallel to the ion channel. Application of this computational modeling strategy, which integrates site-directed affinity labeling with structure-activity knowledge to create a molecular model of the docking of active ligands in the binding pocket, may provide a basis for the design of more selective GABA(A)R modulators with enhanced therapeutic potential.
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Affiliation(s)
- D Berezhnoy
- Laboratory of Molecular Neurobiology, Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA 02118, USA
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43
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Muroi Y, Theusch CM, Czajkowski C, Jackson MB. Distinct structural changes in the GABAA receptor elicited by pentobarbital and GABA. Biophys J 2009; 96:499-509. [PMID: 19167300 DOI: 10.1016/j.bpj.2008.09.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/30/2008] [Indexed: 10/21/2022] Open
Abstract
The barbiturate pentobarbital binds to gamma-aminobutyric acid type A (GABA(A)) receptors, and this interaction plays an important role in the anesthetic action of this drug. Depending on its concentration, pentobarbital can potentiate (approximately 10-100 microM), activate (approximately 100-800 microM), or block (approximately 1-10 mM) the channel, but the mechanisms underlying these three distinct actions are poorly understood. To investigate the drug-induced structural rearrangements in the GABA(A) receptor, we labeled cysteine mutant receptors expressed in Xenopus oocytes with the sulfhydryl-reactive, environmentally sensitive fluorescent probe tetramethylrhodamine-6-maleimide (TMRM). We then used combined voltage clamp and fluorometry to monitor pentobarbital-induced channel activity and local protein movements simultaneously in real time. High concentrations of pentobarbital induced a decrease in TMRM fluorescence (F(TMRM)) of labels tethered to two residues in the extracellular domain (alpha(1)L127C and beta(2)L125C) that have been shown previously to produce an increase in F(TMRM) in response to GABA. Label at beta(2)K274C in the extracellular end of the M2 transmembrane helix reported a small but significant F(TMRM) increase during application of low modulating pentobarbital concentrations, and it showed a much greater F(TMRM) increase at higher concentrations. In contrast, GABA decreased F(TMRM) at this site. These results indicate that GABA and pentobarbital induce different structural rearrangements in the receptor, and thus activate the receptor by different mechanisms. Labels at alpha(1)L127C and beta(2)K274C change their fluorescence by substantial amounts during channel blockade by pentobarbital. In contrast, picrotoxin blockade produces no change in F(TMRM) at these sites, and the pattern of F(TMRM) signals elicited by the antagonist SR95531 differs from that produced by other antagonists. Thus, with either channel block by antagonists or activation by agonists, the structural changes in the GABA(A) receptor protein differ during transitions that are functionally equivalent.
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Affiliation(s)
- Yukiko Muroi
- Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
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Drexler B, Grasshoff C, Rudolph U, Unertl K, Antkowiak B. [The GABA(A) receptor family: possibilities for the development of better anesthetics]. Anaesthesist 2009; 55:287-95. [PMID: 16315024 DOI: 10.1007/s00101-005-0950-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Clinically used anesthetics show amnestic, sedative, hypnotic and immobilizing properties. On a molecular level these drugs affect several receptors in the cell membrane of neurons. By using genetically engineered mice a linkage can now be made between actions on certain receptors and clinically desired and undesired effects. Experiments show that a certain GABA(A) receptor subtype mediates hypnosis and immobility, whereas another subtype is involved in side-effects like sedation and hypothermia. These findings form the basis for the development of new drugs, acting highly specific and with fewer side-effects.
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Affiliation(s)
- B Drexler
- Abteilung für Anaesthesiologie und Intensivmedizin, Universitätsklinikum, Tübingen.
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Nasrallah FA, Griffin JL, Balcar VJ, Rae C. Understanding your inhibitions: effects of GABA and GABAAreceptor modulation on brain cortical metabolism. J Neurochem 2009; 108:57-71. [DOI: 10.1111/j.1471-4159.2008.05742.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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46
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Baburin I, Khom S, Timin E, Hohaus A, Sieghart W, Hering S. Estimating the efficiency of benzodiazepines on GABA(A) receptors comprising gamma1 or gamma2 subunits. Br J Pharmacol 2008; 155:424-33. [PMID: 18604239 PMCID: PMC2451336 DOI: 10.1038/bjp.2008.271] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Background and purpose: Heterologous expression of α1, β2 and γ2S(γ1) subunits produces a mixed population of GABAA receptors containing α1β2 or α1β2γ2S(γ1) subunits. GABA sensitivity (lower in receptors containing γ1 or γ2S subunits) and the potentiation of GABA-activated chloride currents (IGABA) by benzodiazepines (BZDs) are dependent on γ2S(γ1) incorporation. A variable γ subunit incorporation may affect the estimation of IGABA potentiation by BZDs. We propose an approach for estimation of BZD efficiency that accounts for mixed population of α1β2 and α1β2γ2S(γ1) receptors. Experimental approach: We investigated the relation between GABA sensitivity (EC50) and BZD modulation by analysing triazolam-, clotiazepam- and midazolam-induced potentiation of IGABA in Xenopus oocytes under two-microelectrode voltage clamp. Key results: Plotting EC50 versus BZD-induced shifts of GABA concentration-response curves (ΔEC50(BZD)) of oocytes injected with different amounts of α1, β2 and γ2S(γ1) cRNA (1:1:1–1:1:10) revealed a linear regression between γ2S(γ1)-mediated reduction of GABA sensitivity (EC50) and ΔEC50(BZD). The slope factors of the regression were always higher for oocytes expressing α1β2γ1 subunit receptors (1.8±0.1 (triazolam), 1.6±0.1 (clotiazepam), 2.3±0.2 (midazolam)) than for oocytes expressing α1β2γ2S receptors (1.4±0.1 (triazolam), 1.4±0.1 (clotiazepam), 1.3±0.1 (midazolam)). Mutant GABAA receptors (α1β2-R207Cγ2S) with lower GABA sensitivity showed higher drug efficiencies (slope factors=1.1±0.1 (triazolam), 1.1±0.1 (clotiazepam), 1.2±0.1 (midazolam)). Conclusions and implications: Regression analysis enabled the estimation of BZD efficiency when variable mixtures of α1β2 and α1β2γ2S(γ1) receptors are expressed and provided new insights into the γ2S(γ1) dependency of BZD action.
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Affiliation(s)
- I Baburin
- Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria
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Wu TY, Smith CM, Sine SM, Levandoski MM. Morantel allosterically enhances channel gating of neuronal nicotinic acetylcholine alpha 3 beta 2 receptors. Mol Pharmacol 2008; 74:466-75. [PMID: 18458055 DOI: 10.1124/mol.107.044388] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We studied allosteric potentiation of rat alpha3beta2 neuronal nicotinic acetylcholine receptors (nAChRs) by the anthelmintic compound morantel. Macroscopic currents evoked by acetylcholine (ACh) from nAChRs expressed in Xenopus laevis oocytes increase up to 8-fold in the presence of low concentrations of morantel (< or =10 microM); the magnitude of the potentiation depends on both agonist and modulator concentrations. It is noteworthy that the potentiated currents exceed the maximum currents achieved by saturating (millimolar) concentrations of agonist. Studies of macroscopic currents elicited by prolonged drug applications (100-300 s) indicate that morantel does not increase alpha3beta2 receptor activity by reducing slow (> or =1 s) desensitization. Instead, using outside-out patch-clamp recordings, we demonstrate that morantel increases the frequency of single-channel openings and alters the bursting characteristics of the openings in a manner consistent with enhanced channel gating; these results quantitatively explain the macroscopic current potentiation. Morantel is a very weak agonist alone, but we show that the classic competitive antagonist dihydro-beta-erythroidine inhibits morantel-evoked currents noncompetitively, indicating that morantel does not bind to the canonical ACh binding sites.
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Affiliation(s)
- Tse-Yu Wu
- Department of Chemistry, Grinnell College, Grinnell, Iowa 50112, USA
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48
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Abstract
BACKGROUND AND PURPOSE Benzodiazepines (BDZs) are widely used in clinical practice and are known as positive modulators of GABAergic currents. BDZs increase binding affinity and recently they were found to affect GABA(A) receptor gating, including desensitization. Binding and desensitization are also strongly modulated by extracellular pH, a factor that may be severely altered in a pathological brain. It is thus of interest to examine the combined action of BDZ and protons. EXPERIMENTAL APPROACH Pharmacokinetic analysis was based on patch clamp recordings of miniature IPSCs (mIPSCs) and current responses to GABA applications in rat cultured hippocampal neurons. High temporal resolution of currents evoked by exogenous GABA was achieved by using an ultrafast perfusion system (exchange time ca. 80 micros). KEY RESULTS At acidic pH, flurazepam produced a stronger enhancement of mIPSC amplitudes than at physiological pH. At low GABA concentrations, flurazepam markedly enhanced current amplitudes both at normal and acidic pH, but at the latter, the relative effect was larger. In contrast, at saturating GABA concentrations, flurazepam reduced current amplitudes at both pH 7.2 and 6.0. The slowing of deactivation kinetics by flurazepam decreased with GABA concentration, but at pH 6.0, this trend was shifted toward a higher GABA concentration. CONCLUSIONS AND IMPLICATIONS Acidification of extracellular medium may significantly affect the susceptibility of phasic and tonic components of GABAergic currents to modulation by BDZs. Quantitative analysis and model simulations indicate that protons and flurazepam additively affect binding and desensitization of GABA(A) receptors.
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49
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Hsiao B, Mihalak KB, Magleby KL, Luetje CW. Zinc potentiates neuronal nicotinic receptors by increasing burst duration. J Neurophysiol 2007; 99:999-1007. [PMID: 18094103 DOI: 10.1152/jn.01040.2007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Micromolar zinc potentiates neuronal nicotinic acetylcholine receptors (nAChRs) in a subtype-dependent manner. Zinc potentiates receptor function even at saturating agonist concentrations, without altering the receptor desensitization rate. Potentiation could occur through an increase in the number of available receptors, an increase in single-channel current amplitude, or an increase in single-channel open probability. To distinguish among these possibilities, we examined rat neuronal nAChRs expressed in Xenopus oocytes. Blockade of a large fraction of ACh activated alpha4beta4 or alpha4beta2 receptors by the open channel blocker hexamethonium failed to change the extent of potentiation by zinc, suggesting that zinc does not change the number of available receptors. The single-channel amplitudes of ACh (1 microM) activated alpha4beta4 receptors in outside-out patches were similar in the absence and the presence of 100 microM zinc (3.0 +/- 0.1 and 2.9 +/- 0.1 pA, respectively). To determine the effect of zinc on single-channel open probability, we examined alpha4beta4 receptors in cell-attached patches. The open probability at 100 nM ACh (0.011 +/- 0.002) was increased 4.5-fold by 100 microM zinc (0.050 +/- 0.008), accounting for most of the potentiation observed at the whole cell level. The increase in open probability was due to an increase in burst duration, which increased from 207 +/- 38 ms in the absence of zinc to 830 +/- 189 ms in the presence of zinc. Our results suggest that potentiation of neuronal nAChRs by zinc is due to a stabilization of the bursting states of the receptor.
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Affiliation(s)
- Bernard Hsiao
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, FL 33101, USA
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50
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Padgett CL, Lummis SCR. The F-loop of the GABA A receptor gamma2 subunit contributes to benzodiazepine modulation. J Biol Chem 2007; 283:2702-8. [PMID: 17974564 DOI: 10.1074/jbc.m705699200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
GABA(A) receptors can be modulated by benzodiazepines, although these compounds do not directly activate or inhibit the receptors. The prototypic benzodiazepine, diazepam, potentiates responses to GABA in GABA(A) receptors that contain a gamma subunit. Here we have used mutagenesis, radioligand binding, voltage clamp electrophysiology, and homology modeling to probe the role of the F-loop residues Asp(192)-Arg(197) in the GABA(A) receptor gamma(2) subunit in diazepam potentiation of the GABA response. Substitution of all of these residues with Ala and/or a residue with similar chemical properties to the wild type residue decreased the level of diazepam potentiation, and one mutation (D192A) resulted in its complete ablation. None of the mutations changed the GABA EC(50) or the [(3)H]flumazenil binding affinity, suggesting they do not affect GABA or benzodiazepine binding characteristics; we therefore propose that they are involved in the diazepam-mediated conformational change that results in an increased response to GABA. Homology models of the receptor binding pocket in agonist-bound and unbound states suggest that the F-loop is flexible and has different orientations in the two states. Considering our data in relation to these models, we find that the F-loop residues could contribute to hydrogen bond networks and hydrophobic interactions with neighboring residues that change during receptor activation.
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Affiliation(s)
- Claire L Padgett
- Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom
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