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Dharavath RN, Pina-Leblanc C, Tang VM, Sloan ME, Nikolova YS, Pangarov P, Ruocco AC, Shield K, Voineskos D, Blumberger DM, Boileau I, Bozinoff N, Gerretsen P, Vieira E, Melamed OC, Sibille E, Quilty LC, Prevot TD. GABAergic signaling in alcohol use disorder and withdrawal: pathological involvement and therapeutic potential. Front Neural Circuits 2023; 17:1218737. [PMID: 37929054 PMCID: PMC10623140 DOI: 10.3389/fncir.2023.1218737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 09/04/2023] [Indexed: 11/07/2023] Open
Abstract
Alcohol is one of the most widely used substances. Alcohol use accounts for 5.1% of the global disease burden, contributes substantially to societal and economic costs, and leads to approximately 3 million global deaths yearly. Alcohol use disorder (AUD) includes various drinking behavior patterns that lead to short-term or long-lasting effects on health. Ethanol, the main psychoactive molecule acting in alcoholic beverages, directly impacts the GABAergic system, contributing to GABAergic dysregulations that vary depending on the intensity and duration of alcohol consumption. A small number of interventions have been developed that target the GABAergic system, but there are promising future therapeutic avenues to explore. This review provides an overview of the impact of alcohol on the GABAergic system, the current interventions available for AUD that target the GABAergic system, and the novel interventions being explored that in the future could be included among first-line therapies for the treatment of AUD.
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Affiliation(s)
| | - Celeste Pina-Leblanc
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - Victor M. Tang
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Addiction Division, CAMH, Toronto, ON, Canada
- Division of Neurosciences and Clinical Translation, Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Institute of Mental Health Policy Research, CAMH, Toronto, ON, Canada
| | - Matthew E. Sloan
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
- Addiction Division, CAMH, Toronto, ON, Canada
- Division of Neurosciences and Clinical Translation, Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Department of Psychological Clinical Science, University of Toronto Scarborough, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Institute of Mental Health Policy Research, CAMH, Toronto, ON, Canada
| | - Yuliya S. Nikolova
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Peter Pangarov
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
| | - Anthony C. Ruocco
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Temerty Centre for Therapeutic Brain Intervention, CAMH, Toronto, ON, Canada
- Department of Psychology, University of Toronto Scarborough, Toronto, ON, Canada
| | - Kevin Shield
- Institute of Mental Health Policy Research, CAMH, Toronto, ON, Canada
| | - Daphne Voineskos
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Temerty Centre for Therapeutic Brain Intervention, CAMH, Toronto, ON, Canada
| | - Daniel M. Blumberger
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Temerty Centre for Therapeutic Brain Intervention, CAMH, Toronto, ON, Canada
| | - Isabelle Boileau
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Brain Health Imaging Centre, CAMH, Toronto, ON, Canada
| | - Nikki Bozinoff
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada
| | - Philip Gerretsen
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
- Institute of Medical Science, University of Toronto, Toronto, ON, Canada
- Brain Health Imaging Centre, CAMH, Toronto, ON, Canada
| | - Erica Vieira
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Osnat C. Melamed
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada
| | - Etienne Sibille
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Lena C. Quilty
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
| | - Thomas D. Prevot
- Campbell Family Mental Health Research Institute of CAMH, Toronto, ON, Canada
- Department of Psychiatry, University of Toronto, Toronto, ON, Canada
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Gimenez-Gomez P, Le T, Martin GE. Modulation of neuronal excitability by binge alcohol drinking. Front Mol Neurosci 2023; 16:1098211. [PMID: 36866357 PMCID: PMC9971943 DOI: 10.3389/fnmol.2023.1098211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 01/19/2023] [Indexed: 02/16/2023] Open
Abstract
Drug use poses a serious threat to health systems throughout the world. The number of consumers rises every year being alcohol the drug of abuse most consumed causing 3 million deaths (5.3% of all deaths) worldwide and 132.6 million disability-adjusted life years. In this review, we present an up-to-date summary about what is known regarding the global impact of binge alcohol drinking on brains and how it affects the development of cognitive functions, as well as the various preclinical models used to probe its effects on the neurobiology of the brain. This will be followed by a detailed report on the state of our current knowledge of the molecular and cellular mechanisms underlying the effects of binge drinking on neuronal excitability and synaptic plasticity, with an emphasis on brain regions of the meso-cortico limbic neurocircuitry.
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Affiliation(s)
- Pablo Gimenez-Gomez
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, MA, United States
- The Brudnick Neuropsychiatric Research Institute, Worcester, MA, United States
| | - Timmy Le
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, MA, United States
- The Brudnick Neuropsychiatric Research Institute, Worcester, MA, United States
- Graduate Program in Neuroscience, Morningside Graduate School of Biomedical Sciences, UMass Chan Medical School, Worcester, MA, United States
| | - Gilles E. Martin
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, MA, United States
- The Brudnick Neuropsychiatric Research Institute, Worcester, MA, United States
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3
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Gatta E, Camussi D, Auta J, Guidotti A, Pandey SC. Neurosteroids (allopregnanolone) and alcohol use disorder: From mechanisms to potential pharmacotherapy. Pharmacol Ther 2022; 240:108299. [PMID: 36323379 PMCID: PMC9810076 DOI: 10.1016/j.pharmthera.2022.108299] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2022] [Revised: 10/14/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022]
Abstract
Alcohol Use Disorder (AUD) is a multifaceted relapsing disorder that is commonly comorbid with psychiatric disorders, including anxiety. Alcohol exposure produces a plethora of effects on neurobiology. Currently, therapeutic strategies are limited, and only a few treatments - disulfiram, acamprosate, and naltrexone - are available. Given the complexity of this disorder, there is a great need for the identification of novel targets to develop new pharmacotherapy. The GABAergic system, the primary inhibitory system in the brain, is one of the well-known targets for alcohol and is responsible for the anxiolytic effects of alcohol. Interestingly, GABAergic neurotransmission is fine-tuned by neuroactive steroids that exert a regulatory role on several endocrine systems involved in neuropsychiatric disorders including AUD. Mounting evidence indicates that alcohol alters the biosynthesis of neurosteroids, whereas acute alcohol increases and chronic alcohol decreases allopregnanolone levels. Our recent work highlighted that chronic alcohol-induced changes in neurosteroid levels are mediated by epigenetic modifications, e.g., DNA methylation, affecting key enzymes involved in neurosteroid biosynthesis. These changes were associated with changes in GABAA receptor subunit expression, suggesting an imbalance between excitatory and inhibitory signaling in AUD. This review will recapitulate the role of neurosteroids in the regulation of the neuroendocrine system, highlight their role in the observed allostatic load in AUD, and develop a framework from mechanisms to potential pharmacotherapy.
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Affiliation(s)
- Eleonora Gatta
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, Psychiatric Institute, University of Illinois at Chicago, USA
| | - Diletta Camussi
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, Psychiatric Institute, University of Illinois at Chicago, USA
| | - James Auta
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, Psychiatric Institute, University of Illinois at Chicago, USA
| | - Alessandro Guidotti
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, Psychiatric Institute, University of Illinois at Chicago, USA
| | - Subhash C Pandey
- Center for Alcohol Research in Epigenetics, Department of Psychiatry, Psychiatric Institute, University of Illinois at Chicago, USA; Jesse Brown Veterans Affairs Medical Center Chicago, IL 60612, USA.
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4
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Fish KN, Joffe ME. Targeting prefrontal cortex GABAergic microcircuits for the treatment of alcohol use disorder. Front Synaptic Neurosci 2022; 14:936911. [PMID: 36105666 PMCID: PMC9465392 DOI: 10.3389/fnsyn.2022.936911] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Accepted: 07/27/2022] [Indexed: 11/17/2022] Open
Abstract
Developing novel treatments for alcohol use disorders (AUDs) is of paramount importance for improving patient outcomes and alleviating the suffering related to the disease. A better understanding of the molecular and neurocircuit mechanisms through which alcohol alters brain function will be instrumental in the rational development of new efficacious treatments. Clinical studies have consistently associated the prefrontal cortex (PFC) function with symptoms of AUDs. Population-level analyses have linked the PFC structure and function with heavy drinking and/or AUD diagnosis. Thus, targeting specific PFC cell types and neural circuits holds promise for the development of new treatments. Here, we overview the tremendous diversity in the form and function of inhibitory neuron subtypes within PFC and describe their therapeutic potential. We then summarize AUD population genetics studies, clinical neurophysiology findings, and translational neuroscience discoveries. This study collectively suggests that changes in fast transmission through PFC inhibitory microcircuits are a central component of the neurobiological effects of ethanol and the core symptoms of AUDs. Finally, we submit that there is a significant and timely need to examine sex as a biological variable and human postmortem brain tissue to maximize the efforts in translating findings to new clinical treatments.
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Affiliation(s)
| | - Max E. Joffe
- Translational Neuroscience Program, Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, United States
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Bowen MT, George O, Muskiewicz DE, Hall FS. FACTORS CONTRIBUTING TO THE ESCALATION OF ALCOHOL CONSUMPTION. Neurosci Biobehav Rev 2022; 132:730-756. [PMID: 34839930 PMCID: PMC8892842 DOI: 10.1016/j.neubiorev.2021.11.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/05/2021] [Accepted: 11/12/2021] [Indexed: 01/03/2023]
Abstract
Understanding factors that contribute to the escalation of alcohol consumption is key to understanding how an individual transitions from non/social drinking to AUD and to providing better treatment. In this review, we discuss how the way ethanol is consumed as well as individual and environmental factors contribute to the escalation of ethanol consumption from intermittent low levels to consistently high levels. Moreover, we discuss how these factors are modelled in animals. It is clear a vast array of complex, interacting factors influence changes in alcohol consumption. Some of these factors act early in the acquisition of ethanol consumption and initial escalation, while others contribute to escalation of ethanol consumption at a later stage and are involved in the development of alcohol dependence. There is considerable need for more studies examining escalation associated with the formation of dependence and other hallmark features of AUD, especially studies examining mechanisms, as it is of considerable relevance to understanding and treating AUD.
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Affiliation(s)
- Michael T. Bowen
- The University of Sydney, Brain and Mind Centre, Sydney, NSW, 2050, Australia,The University of Sydney, Faculty of Science, School of Psychology, Sydney, NSW, 2006, Australia,Corresponding Author: Michael T. Bowen, Brain and Mind Centre, The University of Sydney, 94 Mallett Street, Camperdown, Sydney, NSW, 2050, Australia,
| | - Olivier George
- Department of Psychology, University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Dawn E. Muskiewicz
- Department of Pharmacology & Experimental Therapeutics, College of Pharmacology and Pharmacological Science, University of Toledo, OH, USA
| | - F. Scott Hall
- Department of Pharmacology & Experimental Therapeutics, College of Pharmacology and Pharmacological Science, University of Toledo, OH, USA
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6
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Modulation of relapse-like drinking in male Sprague-Dawley rats by ligands targeting the α5GABA A receptor. Neuropharmacology 2021; 199:108785. [PMID: 34509495 DOI: 10.1016/j.neuropharm.2021.108785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 08/26/2021] [Accepted: 09/04/2021] [Indexed: 11/20/2022]
Abstract
Preclinical evidence suggests a key role for GABAA receptors containing the α5 subunit (i.e., α5GABAA receptors) in the abuse-related effects of alcohol, including the reinforcing and discriminative stimulus effects, as well as cue-induced alcohol-seeking behavior. However, the contribution of this GABAA receptor subtype to relapse-like drinking behavior remains unknown. The present study evaluated the capacity of ligands targeting α5GABAA receptors to modulate the alcohol deprivation effect (ADE), a model of relapse-like drinking. Groups of Sprague-Dawley rats underwent repeated cycles of long-term access to alcohol solutions (5%, 10%, 20% v/v) and water in the home cage followed by water only deprivation periods. Upon evidence that the ADE could be reliably expressed across cycles, drug treatment was initiated. One group received the α5GABAA receptor-preferring agonist QH-ii-066 and the other group received the α5GABAA receptor-selective inverse agonist L-655,708. At the end of ADE testing, rats underwent testing in the elevated zero maze under vehicle or L-655,708 treatment for assessment of anxiety-like behavior. The ADE was reliably expressed across repeated cycles of alcohol access/deprivation in a subset of rats. Low doses of QH-ii-066 enhanced expression of the ADE; whereas, L-655,708 dose-dependently inhibited expression of the ADE. L-655,708 did not engender anxiogenic effects in the elevated zero maze under the conditions evaluated. These findings suggest a key role for α5GABAA receptor mechanisms in relapse-like drinking. Moreover, they suggest that α5GABAA receptors may represent a novel pharmacological target for the development of medications to prevent or reduce alcohol relapse.
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7
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Daack CW, Yeh D, Busch M, Kliethermes CL. GABAergic regulation of locomotion before and during an ethanol exposure in Drosophila melanogaster. Behav Brain Res 2021; 410:113369. [PMID: 34015397 DOI: 10.1016/j.bbr.2021.113369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 04/30/2021] [Accepted: 05/14/2021] [Indexed: 11/17/2022]
Abstract
Ethanol at low doses induces a locomotor stimulant response across a range of phylogenetically diverse species. In rodents, this response is commonly used as an index of ethanol's disinhibitory, anxiolytic, or reinforcing effects, and its expression is regulated by signaling through a number of conserved neurotransmitter systems. In the current experiments, we asked whether ethanol-induced locomotor stimulation in the fruit fly Drosophila melanogaster might be mediated by ionotropic GABA receptors. We measured basal and ethanol-stimulated locomotion in flies expressing RNAi directed against three known subunits of ionotropic GABA receptors, and also examined the effects of picrotoxin feeding on these behaviors. We found that RNAi-mediated knockdown of a subunit of fly ionotropic GABA receptors, RDL, in all neurons resulted in an increased ethanol-induced locomotor stimulant response, while knockdown of two other subunits, LCCH3 and GRD, did not affect the responses. The effect of pan neuronal RDL knockdown was recapitulated with selective RDL knockdown in cholinergic neurons, and increased ethanol-induced locomotor stimulation was also seen by feeding the GABAA antagonist picrotoxin to flies prior to behavioral testing. However, the increase in ethanol-stimulated locomotion in each of these experiments was largely accounted for by decreased baseline activity. Our results indicate that ionotropic GABA receptors might be a conserved mediator of the locomotor stimulant effects of ethanol, but that alternative experimental approaches will be necessary to disentangle effects of GABAergic manipulations on baseline and ethanol-stimulated locomotion in flies.
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Affiliation(s)
- Calvin W Daack
- Drake University, 318 Olin Hall, 1344 27thStreet, Des Moines, IA, 50311, United States
| | - Derek Yeh
- Drake University, 318 Olin Hall, 1344 27thStreet, Des Moines, IA, 50311, United States
| | - Marc Busch
- Drake University, 318 Olin Hall, 1344 27thStreet, Des Moines, IA, 50311, United States
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8
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Alcohol. Alcohol 2021. [DOI: 10.1016/b978-0-12-816793-9.00001-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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9
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Khatri DK, Choudhary M, Sood A, Singh SB. Anxiety: An ignored aspect of Parkinson’s disease lacking attention. Biomed Pharmacother 2020; 131:110776. [DOI: 10.1016/j.biopha.2020.110776] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 09/08/2020] [Accepted: 09/17/2020] [Indexed: 12/25/2022] Open
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Parker CC, Lusk R, Saba LM. Alcohol Sensitivity as an Endophenotype of Alcohol Use Disorder: Exploring Its Translational Utility between Rodents and Humans. Brain Sci 2020; 10:E725. [PMID: 33066036 PMCID: PMC7600833 DOI: 10.3390/brainsci10100725] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 10/06/2020] [Accepted: 10/09/2020] [Indexed: 12/21/2022] Open
Abstract
Alcohol use disorder (AUD) is a complex, chronic, relapsing disorder with multiple interacting genetic and environmental influences. Numerous studies have verified the influence of genetics on AUD, yet the underlying biological pathways remain unknown. One strategy to interrogate complex diseases is the use of endophenotypes, which deconstruct current diagnostic categories into component traits that may be more amenable to genetic research. In this review, we explore how an endophenotype such as sensitivity to alcohol can be used in conjunction with rodent models to provide mechanistic insights into AUD. We evaluate three alcohol sensitivity endophenotypes (stimulation, intoxication, and aversion) for their translatability across human and rodent research by examining the underlying neurobiology and its relationship to consumption and AUD. We show examples in which results gleaned from rodents are successfully integrated with information from human studies to gain insight in the genetic underpinnings of AUD and AUD-related endophenotypes. Finally, we identify areas for future translational research that could greatly expand our knowledge of the biological and molecular aspects of the transition to AUD with the broad hope of finding better ways to treat this devastating disorder.
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Affiliation(s)
- Clarissa C. Parker
- Department of Psychology and Program in Neuroscience, Middlebury College, Middlebury, VT 05753, USA
| | - Ryan Lusk
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
| | - Laura M. Saba
- Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
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11
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Gruol DL, Melkonian C, Ly K, Sisouvanthong J, Tan Y, Roberts AJ. Alcohol and IL-6 Alter Expression of Synaptic Proteins in Cerebellum of Transgenic Mice with Increased Astrocyte Expression of IL-6. Neuroscience 2020; 442:124-137. [PMID: 32634532 DOI: 10.1016/j.neuroscience.2020.06.043] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 06/03/2020] [Accepted: 06/29/2020] [Indexed: 12/15/2022]
Abstract
Recent studies indicate that neuroimmune factors, including the cytokine interleukin-6 (IL-6), play a role in the CNS actions of alcohol. The cerebellum is a sensitive target of alcohol, but few studies have examined a potential role for neuroimmune factors in the actions of alcohol on this brain region. A number of studies have shown that synaptic transmission, and in particular inhibitory synaptic transmission, is an important cerebellar target of alcohol. IL-6 also alters synaptic transmission, although it is unknown if IL-6 targets are also targets of alcohol. This is an important issue because alcohol induces glial production of IL-6, which could then covertly influence the actions of alcohol. The persistent cerebellar effects of both IL-6 and alcohol typically involve chronic exposure and, presumably, altered gene and protein expression. Thus, in the current studies we tested the possibility that proteins involved in inhibitory and excitatory synaptic transmission in the cerebellum are common targets of alcohol and IL-6. We used transgenic mice that express elevated levels of astrocyte produced IL-6 to model persistently elevated expression of IL-6, as would occur in alcohol use disorders, and a chronic intermittent alcohol exposure/withdrawal paradigm (CIE/withdrawal) that is known to produce alcohol dependence. Multiple cerebellar synaptic proteins were assessed by Western blot. Results show that IL-6 and CIE/withdrawal have both unique and common actions that affect synaptic protein expression. These common targets could provide sites for IL-6/alcohol exposure/withdrawal interactions and play an important role in cerebellar symptoms of alcohol use such as ataxia.
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Affiliation(s)
- Donna L Gruol
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA.
| | - Claudia Melkonian
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Kristine Ly
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jasmin Sisouvanthong
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Yvette Tan
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Amanda J Roberts
- Animal Models Core Facility, The Scripps Research Institute, La Jolla, CA 92037, USA
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12
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Barker JS, Hines RM. Regulation of GABA A Receptor Subunit Expression in Substance Use Disorders. Int J Mol Sci 2020; 21:ijms21124445. [PMID: 32580510 PMCID: PMC7352578 DOI: 10.3390/ijms21124445] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 06/17/2020] [Accepted: 06/19/2020] [Indexed: 01/02/2023] Open
Abstract
The modulation of neuronal cell firing is mediated by the release of the neurotransmitter GABA (γ-aminobuytric acid), which binds to two major families of receptors. The ionotropic GABAA receptors (GABAARs) are composed of five distinct subunits that vary in expression by brain region and cell type. The action of GABA on GABAARs is modulated by a variety of clinically and pharmacologically important drugs such as benzodiazepines and alcohol. Exposure to and abuse of these substances disrupts homeostasis and induces plasticity in GABAergic neurotransmission, often via the regulation of receptor expression. Here, we review the regulation of GABAAR subunit expression in adaptive and pathological plasticity, with a focus on substance use. We examine the factors influencing the expression of GABAAR subunit genes including the regulation of the 5′ and 3′ untranslated regions, variations in DNA methylation, immediate early genes and transcription factors that regulate subunit expression, translational and post-translational modifications, and other forms of receptor regulation beyond expression. Advancing our understanding of the factors regulating GABAAR subunit expression during adaptive plasticity, as well as during substance use and withdrawal will provide insight into the role of GABAergic signaling in substance use disorders, and contribute to the development of novel targeted therapies.
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13
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Janeczek P, Colson N, Dodd PR, Lewohl JM. Sex Differences in the Expression of the α5 Subunit of the GABA A Receptor in Alcoholics with and without Cirrhosis of the Liver. Alcohol Clin Exp Res 2020; 44:423-434. [PMID: 31840824 DOI: 10.1111/acer.14266] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 12/02/2019] [Indexed: 12/18/2022]
Abstract
BACKGROUND Alcohol exposure alters the expression of a large number of genes, resulting in neuronal adaptions and neuronal loss, but the underlying mechanisms are largely unknown. miRNAs are gene repressors that are abundant in the brain. A recent study identified ~ 35 miRNAs that are up-regulated in the prefrontal cortex of human alcoholics and predicted to target genes that are down-regulated in the same region. Although interactions between alcohol-responsive miRNAs and their target genes have been predicted, few studies have validated these predictions. METHODS We measured the expression of GABAA α5 mRNA in the prefrontal and motor cortices of human alcoholics and matched controls using real-time PCR. The expression of miR-203 was measured in a subset of these cases. The predicted interaction of miR-203 and GABRA5 was validated for miR-203 using a luciferase reporter assay. RESULTS In both frontal and motor cortices, the expression of GABAA α5 was significantly lower in cirrhotic alcoholics compared with controls. Further, the pattern of expression between the groups was significantly different between males and females. The expression of miR-203 was higher in the prefrontal cortex of cirrhotic alcoholics compared with controls and uncomplicated alcoholics. These differences were particularly marked in female cases. Cotransfection of GABRA5 with miR-203 in HEK293T cells reduced luciferase reporter activity. CONCLUSION There are sex differences in the expression of GABAA α5 and miR-203 in the brain of human alcoholics which are particularly marked in alcoholics with cirrhosis of the liver. Further, miR-203 may mediate the changes in expression of this GABAA receptor isoform that is brought about by alcohol exposure.
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Affiliation(s)
- Paulina Janeczek
- From the, School of Medical Science, (PJ, NC, JML), Griffith University Gold Coast campus, Southport, Queensland, Australia
| | - Natalie Colson
- From the, School of Medical Science, (PJ, NC, JML), Griffith University Gold Coast campus, Southport, Queensland, Australia
| | - Peter R Dodd
- School of Chemistry and Molecular Biosciences, (PRD), The University of Queensland St Lucia campus, Brisbane, Queensland, Australia
| | - Joanne M Lewohl
- From the, School of Medical Science, (PJ, NC, JML), Griffith University Gold Coast campus, Southport, Queensland, Australia
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14
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Bosse KE, Ghoddoussi F, Eapen AT, Charlton JL, Susick LL, Desai K, Berkowitz BA, Perrine SA, Conti AC. Calcium/calmodulin-stimulated adenylyl cyclases 1 and 8 regulate reward-related brain activity and ethanol consumption. Brain Imaging Behav 2019; 13:396-407. [PMID: 29594872 PMCID: PMC6202255 DOI: 10.1007/s11682-018-9856-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Evidence suggests a predictive link between elevated basal activity within reward-related networks (e.g., cortico-basal ganglia-thalamic networks) and vulnerability for alcoholism. Both calcium channel function and cyclic adenosine monophosphate (cAMP)/protein kinase A-mediated signaling are critical modulators of reward neurocircuitry and reward-related behaviors. Calcium/calmodulin-stimulated adenylyl cyclases (AC) 1 and 8 are sensitive to activity-dependent increases in intracellular calcium and catalyze cAMP production. Therefore, we hypothesized AC1 and 8 regulate brain activity in reward regions of the cortico-basal ganglia-thalamic circuit and that this regulatory influence predicts voluntary ethanol drinking responses. This hypothesis was evaluated by manganese-enhanced magnetic resonance imaging and chronic, intermittent ethanol access procedures. Ethanol-naïve mice with genetic deletion of both AC1 and 8 (DKO mice) exhibited bilateral reductions in baseline activity within cortico-basal ganglia-thalamic regions associated with reward processing compared to wild-type controls (WT, C57BL/6 mice). Significant activity changes were not evident in regions either outside of the cortico-basal ganglia-thalamic network or within the network that are not associated with reward processing. Parallel studies demonstrated that reward network hypoactivity in DKO mice predicted a significant attenuation in consumption and preference levels to escalating ethanol concentrations (12, 20 and 30%) compared to WT mice, an effect that was maintained over extended access (14 sessions) to 20% ethanol. Summarizing, these data support a contribution of AC1 and 8 in cortico-basal ganglia-thalamic activity and the predictive value of this regulatory influence on ethanol drinking behavior, which merits the future evaluation of calcium-stimulated ACs in the neural processes that engender vulnerability to maladaptive alcohol drinking.
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Affiliation(s)
- Kelly E Bosse
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA
| | - Farhad Ghoddoussi
- Department of Anesthesiology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Ajay T Eapen
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA
| | - Jennifer L Charlton
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA
| | - Laura L Susick
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA
| | - Kirt Desai
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI, USA
| | - Bruce A Berkowitz
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, MI, USA
- Department of Ophthalmology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Shane A Perrine
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University School of Medicine, Detroit, MI, USA
| | - Alana C Conti
- Research & Development Service, John D. Dingell VA Medical Center, Detroit, MI, USA.
- Department of Neurosurgery, Wayne State University School of Medicine, Detroit, MI, USA.
- Department of Neurosurgery, Wayne State University, 4646 John R St., Detroit, MI, 48201, USA.
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15
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Abstract
The innate immune system plays a critical role in the ethanol-induced neuroimmune response in the brain. Ethanol initiates the innate immune response via activation of the innate immune receptors Toll-like receptors (TLRs, e.g., TLR4, TLR3, TLR7) and NOD-like receptors (inflammasome NLRs) leading to a release of a plethora of chemokines and cytokines and development of the innate immune response. Cytokines and chemokines can have pro- or anti-inflammatory properties through which they regulate the immune response. In this chapter, we will focus on key cytokines (e.g., IL-1, IL-6, TNF-α) and chemokines (e.g., MCP-1/CCL2) that mediate the ethanol-induced neuroimmune responses. In this regard, we will use IL-1β, as an example cytokine, to discuss the neuromodulatory properties of cytokines on cellular properties and synaptic transmission. We will discuss their involvement through a set of evidence: (1) changes in gene and protein expression following ethanol exposure, (2) association of gene polymorphisms (humans) and alterations in gene expression (animal models) with increased alcohol intake, and (3) modulation of alcohol-related behaviors by transgenic or pharmacological manipulations of chemokine and cytokine systems. Over the last years, our understanding of the molecular mechanisms mediating cytokine- and chemokine-dependent regulation of immune responses has advanced tremendously, and we review evidence pointing to cytokines and chemokines serving as neuromodulators and regulators of neurotransmission.
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Affiliation(s)
- Marisa Roberto
- Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, USA.
| | - Reesha R Patel
- Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, USA
| | - Michal Bajo
- Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, USA
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16
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Chandler CM, Reeves-Darby J, Jones SA, McDonald JA, Li G, Rahman MT, Cook JM, Platt DM. α5GABA A subunit-containing receptors and sweetened alcohol cue-induced reinstatement and active sweetened alcohol self-administration in male rats. Psychopharmacology (Berl) 2019; 236:1797-1806. [PMID: 30637435 PMCID: PMC6606346 DOI: 10.1007/s00213-018-5163-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 12/28/2018] [Indexed: 12/15/2022]
Abstract
RATIONALE GABAA receptors containing the α5 subunit (i.e., α5GABAA receptors) appear to be critically involved in the reinforcing and subjective effects of alcohol. Their role in alcohol relapse remains unknown. OBJECTIVES Pharmacological approaches were used to probe the role of α5GABAA receptors in alcohol seeking induced by re-exposure to a sweetened alcohol-paired cue, as well as in alcohol + sucrose vs. sucrose self-administration. METHODS For reinstatement studies, rats were trained to self-administer alcohol under a fixed-ratio schedule in which responding was maintained by alcohol + sucrose deliveries and an alcohol-paired stimulus. Sweetened alcohol seeking was extinguished by eliminating solution deliveries and the sweetened alcohol-paired stimulus. During reinstatement tests, animals received pretreatments of an α5GABAA inverse agonist (L-655,708) or an agonist (QH-ii-066) prior to sessions in which presentation of the sweetened alcohol-paired stimulus was restored, but no solution was delivered. For self-administration studies, rats were trained to self-administer alcohol + sucrose or sucrose under a fixed-ratio schedule. Once stable, animals received pretreatments of QH-ii-066, L-655,708, the inverse agonist RY-023, or naltrexone. RESULTS L-655,708 attenuated reinstatement of sweetened alcohol seeking by alcohol + sucrose-paired cues; whereas sweetened alcohol-seeking behavior was augmented by QH-ii-066, albeit at different doses in different rats. Both L-655,708 and RY-023 selectively reduced alcohol + sucrose vs. sucrose self-administration. In contrast, naltrexone reduced both alcohol + sucrose and sucrose self-administration; whereas QH-ii-066 enhanced sucrose self-administration only. CONCLUSIONS α5GABAA receptors play a key role in the modulation of sweetened alcohol cue-induced reinstatement, as well as in alcohol + sucrose but not sucrose self-administration. Inverse agonist activity at α5GABAA receptors may offer a novel strategy for both the reduction of problematic drinking and the prevention of relapse.
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Affiliation(s)
- Cassie M. Chandler
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS 39216
| | - Jaren Reeves-Darby
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, Jackson, MS 39216
| | - Sherman A. Jones
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, Jackson, MS 39216
| | - J. Abigail McDonald
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, Jackson, MS 39216
| | - Guanguan Li
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211
| | - Md T. Rahman
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211
| | - James M. Cook
- Department of Chemistry & Biochemistry, University of Wisconsin-Milwaukee, Milwaukee, WI 53211
| | - Donna M. Platt
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS 39216,Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, Jackson, MS 39216,Correspondence: Donna M. Platt, Ph.D.; Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 North State St., Jackson, MS 39216, USA; phone: 601-984-5896; fax: 601-984-5899;
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17
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Berro LF, Rüedi-Bettschen D, Cook JE, Golani LK, Li G, Jahan R, Rashid F, Cook JM, Rowlett JK, Platt DM. GABA A Receptor Subtypes and the Abuse-Related Effects of Ethanol in Rhesus Monkeys: Experiments with Selective Positive Allosteric Modulators. Alcohol Clin Exp Res 2019; 43:791-802. [PMID: 30861153 PMCID: PMC6601614 DOI: 10.1111/acer.14000] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 02/26/2019] [Indexed: 01/31/2023]
Abstract
BACKGROUND Previous studies have investigated α1GABAA and α5GABAA receptor mechanisms in the behavioral effects of ethanol (EtOH) in monkeys. However, genetic studies in humans and preclinical studies with mutant mice suggest a role for α2GABAA and/or α3GABAA receptors in the effects of EtOH. The development of novel positive allosteric modulators (PAMs) with functional selectivity (i.e., selective efficacy) at α2GABAA and α3GABAA receptors allows for probing of these subtypes in preclinical models of the discriminative stimulus and reinforcing effects of EtOH in rhesus macaques. METHODS In discrimination studies, subjects were trained to discriminate EtOH (2 g/kg, intragastrically) from water under a fixed-ratio (FR) schedule of food delivery. In oral self-administration studies, subjects were trained to self-administer EtOH (2% w/v) or sucrose (0.3 to 1% w/v) under an FR schedule of solution availability. RESULTS In discrimination studies, functionally selective PAMs at α2GABAA and α3GABAA (HZ-166) or α3GABAA (YT-III-31) receptors substituted fully (maximum percentage of EtOH-lever responding ≥80%) for the discriminative stimulus effects of EtOH without altering response rates. Full substitution for EtOH also was engendered by a nonselective PAM (triazolam), an α5GABAA -preferring PAM (QH-ii-066) and a PAM at α2GABAA , α3GABAA , and α5GABAA receptors (L-838417). A partial (MRK-696) or an α1GABAA -preferring (zolpidem) PAM only engendered partial substitution (i.e., ~50 to 60% EtOH-lever responding). In self-administration studies, pretreatments with the functionally selective PAMs at α2GABAA and α3GABAA (XHe-II-053 and HZ-166) or α3GABAA (YT-III-31 and YT-III-271) receptors increased EtOH, but not sucrose, drinking at doses that had few, or no, observable sedative-motor effects. CONCLUSIONS Our results confirm prior findings regarding the respective roles of α1GABAA and α5GABAA receptors in the discriminative stimulus effects of EtOH and, further, suggest a key facilitatory role for α3GABAA and potentially α2GABAA receptors in several abuse-related effects of EtOH in monkeys. Moreover, they reveal a potential role for these latter subtypes in EtOH's sedative effects.
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Affiliation(s)
- Lais F. Berro
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | - Daniela Rüedi-Bettschen
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | - Jemma E. Cook
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
| | - Lalit K. Golani
- University of Wisconsin-Milwaukee, Department of Chemistry and Biochemistry, Milwaukee, WI 53201, USA
| | - Guanguan Li
- University of Wisconsin-Milwaukee, Department of Chemistry and Biochemistry, Milwaukee, WI 53201, USA
| | - Rajwana Jahan
- University of Wisconsin-Milwaukee, Department of Chemistry and Biochemistry, Milwaukee, WI 53201, USA
| | - Farjana Rashid
- University of Wisconsin-Milwaukee, Department of Chemistry and Biochemistry, Milwaukee, WI 53201, USA
| | - James M. Cook
- University of Wisconsin-Milwaukee, Department of Chemistry and Biochemistry, Milwaukee, WI 53201, USA
| | - James K. Rowlett
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
- Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA
- Tulane National Primate Research Center, Tulane University School of Medicine, 18703 Three Rivers Road, Covington, LA 70433, USA
| | - Donna M. Platt
- Department of Psychiatry & Human Behavior, University of Mississippi Medical Center, 2500 N. State Street, Jackson, MS, 39216, USA
- Department of Neurobiology & Anatomical Sciences, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA
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18
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Mulligan MK, Abreo T, Neuner SM, Parks C, Watkins CE, Houseal MT, Shapaker TM, Hook M, Tan H, Wang X, Ingels J, Peng J, Lu L, Kaczorowski CC, Bryant CD, Homanics GE, Williams RW. Identification of a Functional Non-coding Variant in the GABA A Receptor α2 Subunit of the C57BL/6J Mouse Reference Genome: Major Implications for Neuroscience Research. Front Genet 2019; 10:188. [PMID: 30984232 PMCID: PMC6449455 DOI: 10.3389/fgene.2019.00188] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2019] [Accepted: 02/21/2019] [Indexed: 12/16/2022] Open
Abstract
GABA type-A (GABA-A) receptors containing the α2 subunit (GABRA2) are expressed in most brain regions and are critical in modulating inhibitory synaptic function. Genetic variation at the GABRA2 locus has been implicated in epilepsy, affective and psychiatric disorders, alcoholism and drug abuse. Gabra2 expression varies as a function of genotype and is modulated by sequence variants in several brain structures and populations, including F2 crosses originating from C57BL/6J (B6J) and the BXD recombinant inbred family derived from B6J and DBA/2J. Here we demonstrate a global reduction of GABRA2 brain protein and mRNA in the B6J strain relative to other inbred strains, and identify and validate the causal mutation in B6J. The mutation is a single base pair deletion located in an intron adjacent to a splice acceptor site that only occurs in the B6J reference genome. The deletion became fixed in B6J between 1976 and 1991 and is now pervasive in many engineered lines, BXD strains generated after 1991, the Collaborative Cross, and the majority of consomic lines. Repair of the deletion using CRISPR-Cas9-mediated gene editing on a B6J genetic background completely restored brain levels of GABRA2 protein and mRNA. Comparison of transcript expression in hippocampus, cortex, and striatum between B6J and repaired genotypes revealed alterations in GABA-A receptor subunit expression, especially in striatum. These results suggest that naturally occurring variation in GABRA2 levels between B6J and other substrains or inbred strains may also explain strain differences in anxiety-like or alcohol and drug response traits related to striatal function. Characterization of the B6J private mutation in the Gabra2 gene is of critical importance to molecular genetic studies in neurobiological research because this strain is widely used to generate genetically engineered mice and murine genetic populations, and is the most widely utilized strain for evaluation of anxiety-like, depression-like, pain, epilepsy, and drug response traits that may be partly modulated by GABRA2 function.
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Affiliation(s)
- Megan K Mulligan
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Timothy Abreo
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Sarah M Neuner
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, TN, United States.,The Jackson Laboratory, Bar Harbor, ME, United States
| | - Cory Parks
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Christine E Watkins
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - M Trevor Houseal
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Thomas M Shapaker
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Michael Hook
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Haiyan Tan
- Departments of Structural Biology and Developmental Neurobiology, Center for Proteomics and Metabolomics, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Xusheng Wang
- Departments of Structural Biology and Developmental Neurobiology, Center for Proteomics and Metabolomics, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Jesse Ingels
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | - Junmin Peng
- Departments of Structural Biology and Developmental Neurobiology, Center for Proteomics and Metabolomics, St. Jude Children's Research Hospital, Memphis, TN, United States
| | - Lu Lu
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
| | | | - Camron D Bryant
- Laboratory of Addiction Genetics, Department of Pharmacology and Experimental Therapeutics and Psychiatry, Boston University School of Medicine, Boston, MA, United States
| | - Gregg E Homanics
- Departments of Anesthesiology and Perioperative Medicine, Neurobiology, and Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA, United States
| | - Robert W Williams
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, United States
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19
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Rhinehart EM, Nentwig TB, Wilson DE, Leonard KT, Chaney BN, Grisel JE. Sex and β-Endorphin Influence the Effects of Ethanol on Limbic Gabra2 Expression in a Mouse Binge Drinking Model. Front Genet 2018; 9:567. [PMID: 30555510 PMCID: PMC6281685 DOI: 10.3389/fgene.2018.00567] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 11/06/2018] [Indexed: 11/13/2022] Open
Abstract
Binge drinking is a widespread problem linked to increased risk for alcohol-related complications, including development of alcohol use disorders. In the last decade, binge drinking has increased significantly, specifically in women. Clinically, sexually dimorphic effects of alcohol are well-characterized, however, the underlying mechanisms for these dimorphisms in the physiological and behavioral effects of alcohol are poorly understood. Among its many effects, alcohol consumption reduces anxiety via the inhibitory neurotransmitter GABA, most likely acting upon receptors containing the α-2 subunit (Gabra2). Previous research from our laboratory indicates that female mice lacking the endogenous opioid peptide β-endorphin (βE) have an overactive stress axis and enhanced anxiety-like phenotype, coupled with increased binge-like alcohol consumption. Because βE works via GABA signaling to reduce anxiety, we sought to determine whether sexually dimorphic binge drinking behavior in βE deficient mice is coupled with differences in CNS Gabra2 expression. To test this hypothesis, we used βE knock-out mice in a "drinking in the dark" model where adult male and female C57BL/6J controls (βE +/+) and βE deficient (βE -/-; B6.129S2-Pomctm1Low/J) mice were provided with one bottle of 20% ethanol (EtOH) and one of water (EtOH drinkers) or two bottles of water (water drinkers) 3 h into the dark cycle for four consecutive days. Following a binge test on day 4, limbic tissue was collected and frozen for subsequent qRT-PCR analysis of Gabra2 mRNA expression. Water-drinking βE +/+ females expressed more Gabra2 in central nucleus of the amygdala and the bed nucleus of the stria terminalis than males, but this sex difference was absent in the βE -/- mice. Genotype alone had no effect on alcohol consumption or drug-induced increase in Gabra2 expression. In contrast, βE expression had bi-directional effects in females: in wildtypes, Gabra2 mRNA was reduced by binge EtOH consumption, while EtOH increased expression in βE -/- females to levels commensurate with drug-naïve βE +/+ females. These results support the contention that βE plays a role in sexually dimorphic binge-like EtOH consumption, perhaps through differential expression of GABAA α2 subunits in limbic structures known to play key roles in the regulation of stress and anxiety.
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Affiliation(s)
- Erin M Rhinehart
- Department of Biology, Susquehanna University, Selinsgrove, PA, United States
| | - Todd B Nentwig
- Department of Psychology, Neuroscience Program, Bucknell University, Lewisburg, PA, United States
| | - Diane E Wilson
- Department of Biology, Susquehanna University, Selinsgrove, PA, United States
| | - Kiarah T Leonard
- Department of Psychology, Neuroscience Program, Bucknell University, Lewisburg, PA, United States
| | - Bernie N Chaney
- Department of Psychology, Neuroscience Program, Bucknell University, Lewisburg, PA, United States
| | - Judith E Grisel
- Department of Psychology, Neuroscience Program, Bucknell University, Lewisburg, PA, United States
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20
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Gruol DL, Huitron-Resendiz S, Roberts AJ. Altered brain activity during withdrawal from chronic alcohol is associated with changes in IL-6 signal transduction and GABAergic mechanisms in transgenic mice with increased astrocyte expression of IL-6. Neuropharmacology 2018; 138:32-46. [PMID: 29787738 DOI: 10.1016/j.neuropharm.2018.05.024] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 04/25/2018] [Accepted: 05/17/2018] [Indexed: 10/16/2022]
Abstract
Interleukin-6 (IL-6) is an important neuroimmune factor that is increased in the brain by alcohol exposure/withdrawal and is thought to play a role in the actions of alcohol on the brain. To gain insight into IL-6/alcohol/withdrawal interactions and how these interactions affect the brain, we are studying the effects of chronic binge alcohol exposure on transgenic mice that express elevated levels of IL-6 in the brain due to increased astrocyte expression (IL-6 tg) and their non-transgenic (non-tg) littermate controls. IL-6/alcohol/withdrawal interactions were identified by genotypic differences in spontaneous brain activity in electroencephalogram (EEG) recordings from the mice, and by Western blot analysis of protein activation or expression in hippocampus obtained from the mice after the final alcohol withdrawal period. Results from EEG studies showed frequency dependent genotypic differences in brain activity during withdrawal. For EEG frequencies that were affected by alcohol exposure/withdrawal in both genotypes, the nature of the effect was similar, but differed across withdrawal cycles. Differences between IL-6 tg and non-tg mice were also observed in Western blot studies of the activated form of STAT3 (phosphoSTAT3), a signal transduction partner of IL-6, and subunits of GABAA receptors (GABAAR). Regression analysis revealed that pSTAT3 played a more prominent role during withdrawal in the IL-6 tg mice than in the non-tg mice, and that the role of GABAAR alpha-5 and GABAAR alpha-1 in brain activity varied across genotype and withdrawal. Taken together, our results suggest that IL-6 can significantly impact mechanisms involved in alcohol withdrawal.
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Affiliation(s)
- Donna L Gruol
- Neuroscience Department, The Scripps Research Institute, La Jolla, CA, 92037, USA.
| | | | - Amanda J Roberts
- Animal Models Core Facility, The Scripps Research Institute, La Jolla, CA, 92037, USA
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21
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The Cerebellar GABA AR System as a Potential Target for Treating Alcohol Use Disorder. Handb Exp Pharmacol 2018; 248:113-156. [PMID: 29736774 DOI: 10.1007/164_2018_109] [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] [Indexed: 12/14/2022]
Abstract
In the brain, fast inhibitory neurotransmission is mediated primarily by the ionotropic subtype of the gamma-aminobutyric acid (GABA) receptor subtype A (GABAAR). It is well established that the brain's GABAAR system mediates many aspects of neurobehavioral responses to alcohol (ethanol; EtOH). Accordingly, in both preclinical studies and some clinical scenarios, pharmacologically targeting the GABAAR system can alter neurobehavioral responses to acute and chronic EtOH consumption. However, many of the well-established interactions of EtOH and the GABAAR system have been identified at concentrations of EtOH ([EtOH]) that would only occur during abusive consumption of EtOH (≥40 mM), and there are still inadequate treatment options for prevention of or recovery from alcohol use disorder (AUD, including abuse and dependence). Accordingly, there is a general acknowledgement that more research is needed to identify and characterize: (1) neurobehavioral targets of lower [EtOH] and (2) associated brain structures that would involve such targets in a manner that may influence the development and maintenance of AUDs.Nearly 15 years ago it was discovered that the GABAAR system of the cerebellum is highly sensitive to EtOH, responding to concentrations as low as 10 mM (as would occur in the blood of a typical adult human after consuming 1-2 standard units of EtOH). This high sensitivity to EtOH, which likely mediates the well-known motor impairing effects of EtOH, combined with recent advances in our understanding of the role of the cerebellum in non-motor, cognitive/emotive/reward processes has renewed interest in this system in the specific context of AUD. In this chapter we will describe recent advances in our understanding of cerebellar processing, actions of EtOH on the cerebellar GABAAR system, and the potential relationship of such actions to the development of AUD. We will finish with speculation about how cerebellar specific GABAAR ligands might be effective pharmacological agents for treating aspects of AUD.
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22
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Chandler CM, Overton JS, Rüedi-Bettschen D, Platt DM. GABA A Receptor Subtype Mechanisms and the Abuse-Related Effects of Ethanol: Genetic and Pharmacological Evidence. Handb Exp Pharmacol 2018; 248:3-27. [PMID: 29204713 DOI: 10.1007/164_2017_80] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Ethanol's reinforcing and subjective effects, as well as its ability to induce relapse, are powerful factors contributing to its widespread use and abuse. A significant mediator of these behavioral effects is the GABAA receptor system. GABAA receptors are the target for γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the CNS. Structurally, they are pentameric, transmembrane chloride ion channels comprised of subunits from at least eight different families of distinct proteins. The contribution of different GABAA subunits to ethanol's diverse abuse-related effects is not clear and remains an area of research focus. This chapter details the clinical and preclinical findings supporting roles for different α, β, γ, and δ subunit-containing GABAA receptors in ethanol's reinforcing, subjective/discriminative stimulus, and relapse-inducing effects. The reinforcing properties of ethanol have been studied the most systematically, and convergent preclinical evidence suggests a key role for the α5 subunit in those effects. Regarding ethanol's subjective/discriminative stimulus effects, clinical and genetic findings support a primary role for the α2 subunit, whereas preclinical evidence implicates the α5 subunit. At present, too few studies investigating ethanol relapse exist to make any solid conclusions regarding the role of specific GABAA subunits in this abuse-related effect.
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Affiliation(s)
- Cassie M Chandler
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA
| | - John S Overton
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Daniela Rüedi-Bettschen
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA
| | - Donna M Platt
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS, USA.
- Department of Psychiatry and Human Behavior, University of Mississippi Medical Center, Jackson, MS, USA.
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23
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Blednov YA, Borghese CM, Ruiz CI, Cullins MA, Da Costa A, Osterndorff-Kahanek EA, Homanics GE, Harris RA. Mutation of the inhibitory ethanol site in GABA A ρ1 receptors promotes tolerance to ethanol-induced motor incoordination. Neuropharmacology 2017. [PMID: 28623169 DOI: 10.1016/j.neuropharm.2017.06.013] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Genes encoding the ρ1/2 subunits of GABAA receptors have been associated with alcohol (ethanol) dependence in humans, and ρ1 was also shown to regulate some of the behavioral effects of ethanol in animal models. Ethanol inhibits GABA-mediated responses in wild-type (WT) ρ1, but not ρ1(T6'Y) mutant receptors expressed in Xenopus laevis oocytes, indicating the presence of an inhibitory site for ethanol in the second transmembrane helix. In this study, we found that ρ1(T6'Y) receptors expressed in oocytes display overall normal responses to GABA, the endogenous GABA modulator (zinc), and partial agonists (β-alanine and taurine). We generated ρ1 (T6'Y) knockin (KI) mice using CRISPR/Cas9 to test the behavioral importance of the inhibitory actions of ethanol on this receptor. Both ρ1 KI and knockout (KO) mice showed faster recovery from acute ethanol-induced motor incoordination compared to WT mice. Both KI and KO mutant strains also showed increased tolerance to motor impairment produced by ethanol. The KI mice did not differ from WT mice in other behavioral actions, including ethanol intake and preference, conditioned taste aversion to ethanol, and duration of ethanol-induced loss of righting reflex. WT and KI mice did not differ in levels of ρ1 or ρ2 mRNA in cerebellum or in ethanol clearance. Our findings indicate that the inhibitory site for ethanol in GABAA ρ1 receptors regulates acute functional tolerance to moderate ethanol intoxication. We note that low sensitivity to alcohol intoxication has been linked to risk for development of alcohol dependence in humans.
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Affiliation(s)
- Yuri A Blednov
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States
| | - Cecilia M Borghese
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States
| | - Carlos I Ruiz
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States
| | - Madeline A Cullins
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States
| | - Adriana Da Costa
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States
| | | | - Gregg E Homanics
- University of Pittsburgh, Departments of Anesthesiology, Neurobiology, and Pharmacology & Chemical Biology, Pittsburgh, PA 15261, United States
| | - R Adron Harris
- The University of Texas at Austin, Waggoner Center for Alcohol and Addiction Research, Austin, TX 78712, United States.
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Nikoui V, Ostadhadi S, Azhand P, Zolfaghari S, Amiri S, Foroohandeh M, Motevalian M, Sharifi AM, Bakhtiarian A. The effect of nitrazepam on depression and curiosity in behavioral tests in mice: The role of potassium channels. Eur J Pharmacol 2016; 791:369-376. [DOI: 10.1016/j.ejphar.2016.09.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/06/2016] [Accepted: 09/07/2016] [Indexed: 02/06/2023]
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Stephens DN, King SL, Lambert JJ, Belelli D, Duka T. GABAAreceptor subtype involvement in addictive behaviour. GENES BRAIN AND BEHAVIOR 2016; 16:149-184. [DOI: 10.1111/gbb.12321] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Revised: 07/19/2016] [Accepted: 08/15/2016] [Indexed: 12/17/2022]
Affiliation(s)
| | - S. L. King
- School of Psychology; University of Sussex; Brighton UK
| | - J. J. Lambert
- Division of Neuroscience; University of Dundee; Dundee UK
| | - D. Belelli
- Division of Neuroscience; University of Dundee; Dundee UK
| | - T. Duka
- School of Psychology; University of Sussex; Brighton UK
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Mayfield J, Arends MA, Harris RA, Blednov YA. Genes and Alcohol Consumption: Studies with Mutant Mice. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2016; 126:293-355. [PMID: 27055617 PMCID: PMC5302130 DOI: 10.1016/bs.irn.2016.02.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
In this chapter, we review the effects of global null mutant and overexpressing transgenic mouse lines on voluntary self-administration of alcohol. We examine approximately 200 publications pertaining to the effects of 155 mouse genes on alcohol consumption in different drinking models. The targeted genes vary in function and include neurotransmitter, ion channel, neuroimmune, and neuropeptide signaling systems. The alcohol self-administration models include operant conditioning, two- and four-bottle choice continuous and intermittent access, drinking in the dark limited access, chronic intermittent ethanol, and scheduled high alcohol consumption tests. Comparisons of different drinking models using the same mutant mice are potentially the most informative, and we will highlight those examples. More mutants have been tested for continuous two-bottle choice consumption than any other test; of the 137 mouse genes examined using this model, 97 (72%) altered drinking in at least one sex. Overall, the effects of genetic manipulations on alcohol drinking often depend on the sex of the mice, alcohol concentration and time of access, genetic background, as well as the drinking test.
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Affiliation(s)
- J Mayfield
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, United States
| | - M A Arends
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, La Jolla, CA, United States
| | - R A Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, United States.
| | - Y A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX, United States
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Raud S, Reimets R, Loomets M, Sütt S, Altpere A, Visnapuu T, Innos J, Luuk H, Plaas M, Volke V, Vasar E. Deletion of the Wolfram syndrome-related gene Wfs1 results in increased sensitivity to ethanol in female mice. Neuropharmacology 2015; 95:59-67. [DOI: 10.1016/j.neuropharm.2015.02.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 02/13/2015] [Accepted: 02/15/2015] [Indexed: 10/23/2022]
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Blednov YA, Benavidez JM, Black M, Mayfield J, Harris RA. Role of interleukin-1 receptor signaling in the behavioral effects of ethanol and benzodiazepines. Neuropharmacology 2015; 95:309-20. [PMID: 25839897 DOI: 10.1016/j.neuropharm.2015.03.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 02/10/2015] [Accepted: 03/16/2015] [Indexed: 12/20/2022]
Abstract
Gene expression studies identified the interleukin-1 receptor type I (IL-1R1) as part of a pathway associated with a genetic predisposition to high alcohol consumption, and lack of the endogenous IL-1 receptor antagonist (IL-1ra) strongly reduced ethanol intake in mice. Here, we compared ethanol-mediated behaviors in mice lacking Il1rn or Il1r1. Deletion of Il1rn (the gene encoding IL-1ra) increases sensitivity to the sedative/hypnotic effects of ethanol and flurazepam and reduces severity of acute ethanol withdrawal. Conversely, deletion of Il1r1 (the gene encoding the IL-1 receptor type I, IL-1R1) reduces sensitivity to the sedative effects of ethanol and flurazepam and increases the severity of acute ethanol withdrawal. The sedative effects of ketamine and pentobarbital were not altered in the knockout (KO) strains. Ethanol intake and preference were not changed in mice lacking Il1r1 in three different tests of ethanol consumption. Recovery from ethanol-induced motor incoordination was only altered in female mice lacking Il1r1. Mice lacking Il1rn (but not Il1r1) showed increased ethanol clearance and decreased ethanol-induced conditioned taste aversion. The increased ethanol- and flurazepam-induced sedation in Il1rn KO mice was decreased by administration of IL-1ra (Kineret), and pre-treatment with Kineret also restored the severity of acute ethanol withdrawal. Ethanol-induced sedation and withdrawal severity were changed in opposite directions in the null mutants, indicating that these responses are likely regulated by IL-1R1 signaling, whereas ethanol intake and preference do not appear to be solely regulated by this pathway.
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Affiliation(s)
- Yuri A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jillian M Benavidez
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - Mendy Black
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - Jody Mayfield
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA.
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Bajo M, Herman MA, Varodayan FP, Oleata CS, Madamba SG, Harris RA, Blednov YA, Roberto M. Role of the IL-1 receptor antagonist in ethanol-induced regulation of GABAergic transmission in the central amygdala. Brain Behav Immun 2015; 45:189-97. [PMID: 25479427 PMCID: PMC4405101 DOI: 10.1016/j.bbi.2014.11.011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/13/2014] [Accepted: 11/24/2014] [Indexed: 12/26/2022] Open
Abstract
The IL-1 receptor antagonist (IL-1ra), encoded by the Il1rn gene, is an endogenous antagonist of the IL-1 receptor. Studies of Il1rn knockout (KO) and wild type (WT) mice identified differences in several ethanol-related behaviors, some of which may be mediated by GABAergic transmission in the central nucleus of the amygdala (CeA). In this study we examined phasic (both evoked and spontaneous) and tonic GABAergic transmission in the CeA of Il1rn KO and WT mice and the ethanol sensitivity of these GABAergic synapses. The mean amplitude of baseline evoked GABAA-inhibitory postsynaptic potentials (IPSPs), and the baseline frequency of spontaneous GABAA-inhibitory postsynaptic currents (sIPSCs), but not the frequency of miniature GABAA-IPSCs (mIPSCs), were significantly increased in KO compared to WT mice, indicating enhanced presynaptic action potential-dependent GABA release in the CeA of KO mice. In KO mice, we also found a cell-type specific switch in the ongoing tonic GABAA receptor conductance such that the tonic conductance in low threshold bursting (LTB) neurons is lost and a tonic conductance in late spiking (LS) neurons appears. Notably, the ethanol-induced facilitation of evoked and spontaneous GABA release was lost in most of the CeA neurons from KO compared to WT mice. Ethanol superfusion increased the sIPSC rise and decay times in both KO and WT mice, suggesting ethanol-induced postsynaptic effects. The pretreatment of CeA slices with exogenous IL-1ra (Kineret; 100ng/ml) returned sIPSC frequency in KO mice to the levels found in WT. Importantly, Kineret also restored ethanol-induced potentiation of the sIPSC frequency in the KO mice. These results show that IL-1ra regulates baseline GABAergic transmission in the CeA and is critical for the ethanol effects at these synapses.
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Affiliation(s)
- M Bajo
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
| | - M A Herman
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - F P Varodayan
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - C S Oleata
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - S G Madamba
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - R A Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - Y A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, TX 78712, USA
| | - M Roberto
- Committee on the Neurobiology of Addictive Disorders, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.
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Olsen RW. Allosteric ligands and their binding sites define γ-aminobutyric acid (GABA) type A receptor subtypes. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2015; 73:167-202. [PMID: 25637441 DOI: 10.1016/bs.apha.2014.11.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
GABAA receptors (GABA(A)Rs) mediate rapid inhibitory transmission in the brain. GABA(A)Rs are ligand-gated chloride ion channel proteins and exist in about a dozen or more heteropentameric subtypes exhibiting variable age and brain regional localization and thus participation in differing brain functions and diseases. GABA(A)Rs are also subject to modulation by several chemotypes of allosteric ligands that help define structure and function, including subtype definition. The channel blocker picrotoxin identified a noncompetitive channel blocker site in GABA(A)Rs. This ligand site is located in the transmembrane channel pore, whereas the GABA agonist site is in the extracellular domain at subunit interfaces, a site useful for low energy coupled conformational changes of the functional channel domain. Two classes of pharmacologically important allosteric modulatory ligand binding sites reside in the extracellular domain at modified agonist sites at other subunit interfaces: the benzodiazepine site and the high-affinity, relevant to intoxication, ethanol site. The benzodiazepine site is specific for certain GABA(A)R subtypes, mainly synaptic, while the ethanol site is found at a modified benzodiazepine site on different, extrasynaptic, subtypes. In the transmembrane domain are allosteric modulatory ligand sites for diverse chemotypes of general anesthetics: the volatile and intravenous agents, barbiturates, etomidate, propofol, long-chain alcohols, and neurosteroids. The last are endogenous positive allosteric modulators. X-ray crystal structures of prokaryotic and invertebrate pentameric ligand-gated ion channels, and the mammalian GABA(A)R protein, allow homology modeling of GABA(A)R subtypes with the various ligand sites located to suggest the structure and function of these proteins and their pharmacological modulation.
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Affiliation(s)
- Richard W Olsen
- Department of Molecular & Medical Pharmacology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
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31
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Barker JM, Taylor JR. Habitual alcohol seeking: modeling the transition from casual drinking to addiction. Neurosci Biobehav Rev 2014; 47:281-94. [PMID: 25193245 PMCID: PMC4258136 DOI: 10.1016/j.neubiorev.2014.08.012] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 07/17/2014] [Accepted: 08/25/2014] [Indexed: 12/29/2022]
Abstract
The transition from goal-directed actions to habitual ethanol seeking models the development of addictive behavior that characterizes alcohol use disorders. The progression to habitual ethanol-seeking behavior occurs more rapidly than for natural rewards, suggesting that ethanol may act on habit circuit to drive the loss of behavioral flexibility. This review will highlight recent research that has focused on the formation and expression of habitual ethanol seeking, and the commonalities and distinctions between ethanol and natural reward-seeking habits, with the goal of highlighting important, understudied research areas that we believe will lead toward the development of novel treatment and prevention strategies for uncontrolled drinking.
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Affiliation(s)
- Jacqueline M Barker
- Department of Psychiatry, Yale University School of Medicine, Ribicoff Labs, New Haven, CT, USA; Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT, USA
| | - Jane R Taylor
- Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, CT, USA.
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Jin Z, Bhandage AK, Bazov I, Kononenko O, Bakalkin G, Korpi ER, Birnir B. Expression of specific ionotropic glutamate and GABA-A receptor subunits is decreased in central amygdala of alcoholics. Front Cell Neurosci 2014; 8:288. [PMID: 25278838 PMCID: PMC4165314 DOI: 10.3389/fncel.2014.00288] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 08/29/2014] [Indexed: 01/20/2023] Open
Abstract
The central amygdala (CeA) has a role for mediating fear and anxiety responses. It is also involved in emotional imbalance caused by alcohol abuse and dependence and in regulating relapse to alcohol abuse. Growing evidences suggest that excitatory glutamatergic and inhibitory γ-aminobutyric acid-ergic (GABAergic) transmissions in the CeA are affected by chronic alcohol exposure. Human post-mortem CeA samples from male alcoholics (n = 9) and matched controls (n = 9) were assayed for the expression level of ionotropic glutamate and GABA-A receptors subunit mRNAs using quantitative real-time reverse transcription-PCR (RT-qPCR). Our data revealed that out of the 16 ionotropic glutamate receptor subunits, mRNAs encoding two AMPA [2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propanoic acid] receptor subunits GluA1 and GluA4; one kainate receptor subunit GluK2; one NMDA (N-methyl-D-aspartate) receptor subunit GluN2D and one delta receptor subunit GluD2 were significantly decreased in the CeA of alcoholics. In contrast, of the 19 GABA-A receptor subunits, only the mRNA encoding the α2 subunit was significantly down-regulated in the CeA of the alcoholics as compared with control subjects. Our findings imply that the down-regulation of specific ionotropic glutamate and GABA-A receptor subunits in the CeA of alcoholics may represent one of the molecular substrates underlying the new balance between excitatory and inhibitory neurotransmission in alcohol dependence.
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Affiliation(s)
- Zhe Jin
- Molecular Physiology and Neuroscience Unit, Neuroscience, Biomedical Center, Uppsala University Uppsala, Sweden
| | - Amol K Bhandage
- Molecular Physiology and Neuroscience Unit, Neuroscience, Biomedical Center, Uppsala University Uppsala, Sweden
| | - Igor Bazov
- Division of Biological Research on Drug Dependence, Department of Pharmaceutical Biosciences, Uppsala University Uppsala, Sweden
| | - Olga Kononenko
- Division of Biological Research on Drug Dependence, Department of Pharmaceutical Biosciences, Uppsala University Uppsala, Sweden
| | - Georgy Bakalkin
- Division of Biological Research on Drug Dependence, Department of Pharmaceutical Biosciences, Uppsala University Uppsala, Sweden
| | - Esa R Korpi
- Pharmacology, Institute of Biomedicine, University of Helsinki Helsinki, Finland
| | - Bryndis Birnir
- Molecular Physiology and Neuroscience Unit, Neuroscience, Biomedical Center, Uppsala University Uppsala, Sweden
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Liang J, Olsen RW. Alcohol use disorders and current pharmacological therapies: the role of GABA(A) receptors. Acta Pharmacol Sin 2014; 35:981-93. [PMID: 25066321 PMCID: PMC4125717 DOI: 10.1038/aps.2014.50] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2014] [Accepted: 05/16/2014] [Indexed: 12/18/2022] Open
Abstract
Alcohol use disorders (AUD) are defined as alcohol abuse and alcohol dependence, which create large problems both for society and for the drinkers themselves. To date, no therapeutic can effectively solve these problems. Understanding the underlying mechanisms leading to AUD is critically important for developing effective and safe pharmacological therapies. Benzodiazepines (BZs) are used to reduce the symptoms of alcohol withdrawal syndrome. However, frequent use of BZs causes cross-tolerance, dependence, and cross-addiction to alcohol. The FDA-approved naltrexone and acamprosate have shown mixed results in clinical trials. Naltrexone is effective to treat alcohol dependence (decreased length and frequency of drinking bouts), but its severe side effects, including withdrawal symptoms, are difficult to overcome. Acamprosate showed efficacy for treating alcohol dependence in European trials, but two large US trials have failed to confirm the efficacy. Another FDA-approved medication, disulfiram, does not diminish craving, and it causes a peripheral neuropathy. Kudzu is the only natural medication mentioned by the National Institute on Alcohol Abuse and Alcoholism, but its mechanisms of action are not yet established. It has been recently shown that dihydromyricetin, a flavonoid purified from Hovenia, has unique effects on GABAA receptors and blocks ethanol intoxication and withdrawal in alcoholic animal models. In this article, we review the role of GABAA receptors in the treatment of AUD and currently available and potentially novel pharmacological agents.
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Affiliation(s)
- Jing Liang
- Department of Molecular & Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Richard W Olsen
- Department of Molecular & Medical Pharmacology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
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Mutations in the Gabrb1 gene promote alcohol consumption through increased tonic inhibition. Nat Commun 2014; 4:2816. [PMID: 24281383 PMCID: PMC3843143 DOI: 10.1038/ncomms3816] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 10/24/2013] [Indexed: 01/06/2023] Open
Abstract
Alcohol-dependence is a common, complex and debilitating disorder with genetic and environmental influences. Here we show that alcohol consumption increases following mutations to the γ-aminobutyric acidA receptor (GABAAR) β1 subunit gene (Gabrb1). Using N-ethyl-N-nitrosourea mutagenesis on an alcohol-averse background (F1 BALB/cAnN × C3H/HeH), we develop a mouse model exhibiting strong heritable preference for ethanol resulting from a dominant mutation (L285R) in Gabrb1. The mutation causes spontaneous GABA ion channel opening and increases GABA sensitivity of recombinant GABAARs, coupled to increased tonic currents in the nucleus accumbens, a region long-associated with alcohol reward. Mutant mice work harder to obtain ethanol, and are more sensitive to alcohol intoxication. Another spontaneous mutation (P228H) in Gabrb1 also causes high ethanol consumption accompanied by spontaneous GABA ion channel opening and increased accumbal tonic current. Our results provide a new and important link between GABAAR function and increased alcohol consumption that could underlie some forms of alcohol abuse.
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Neural basis of benzodiazepine reward: requirement for α2 containing GABAA receptors in the nucleus accumbens. Neuropsychopharmacology 2014; 39:1805-15. [PMID: 24553732 PMCID: PMC4059902 DOI: 10.1038/npp.2014.41] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 01/15/2014] [Accepted: 01/21/2014] [Indexed: 11/09/2022]
Abstract
Despite long-standing concerns regarding the abuse liability of benzodiazepines, the mechanisms underlying properties of benzodiazepines that may be relevant to abuse are still poorly understood. Earlier studies showed that compounds selective for α1-containing GABAA receptors (α1GABAARs) are abused by humans and self-administered by animals, and that these receptors may underlie a preference for benzodiazepines as well as neuroplastic changes observed in the ventral tegmental area following benzodiazepine administration. There is some evidence, however, that even L-838, 417, a compound with antagonistic properties at α1GABAARs and agonistic properties at the other three benzodiazepine-sensitive GABAA receptor subtypes, is self-administered, and that the α2GABAARs may have a role in benzodiazepine-induced reward enhancement. Using a two-bottle choice drinking paradigm to evaluate midazolam preference and an intracranial self-stimulation (ICSS) paradigm to evaluate the impact of midazolam on reward enhancement, we demonstrated that mice carrying a histidine-to-arginine point mutation in the α2 subunit which renders it insensitive to benzodiazepines (α2(H101R) mice) did not prefer midazolam and did not show midazolam-induced reward enhancement in ICSS, in contrast to wild-type controls, suggesting that α2GABAARs are necessary for the reward enhancing effects and preference for oral benzodiazepines. Through a viral-mediated knockdown of α2GABAARs in the nucleus accumbens (NAc), we demonstrated that α2 in the NAc is necessary for the preference for midazolam. Findings imply that α2GABAARs in the NAc are involved in at least some reward-related properties of benzodiazepines, which might partially underlie repeated drug-taking behavior.
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Morozova TV, Mackay TFC, Anholt RRH. Genetics and genomics of alcohol sensitivity. Mol Genet Genomics 2014; 289:253-69. [PMID: 24395673 PMCID: PMC4037586 DOI: 10.1007/s00438-013-0808-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 12/22/2013] [Indexed: 01/20/2023]
Abstract
Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.
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Affiliation(s)
- Tatiana V. Morozova
- Department of Biological Sciences and W. M. Keck Center for Behavioral Biology, North Carolina State University, Box 7617, Raleigh, NC 27695-7617 USA
| | - Trudy F. C. Mackay
- Department of Biological Sciences and W. M. Keck Center for Behavioral Biology, North Carolina State University, Box 7617, Raleigh, NC 27695-7617 USA
| | - Robert R. H. Anholt
- Department of Biological Sciences and W. M. Keck Center for Behavioral Biology, North Carolina State University, Box 7617, Raleigh, NC 27695-7617 USA
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Sawyer EK, Moran C, Sirbu MH, Szafir M, Van Linn M, Namjoshi O, Tiruveedhula VVNPB, Cook JM, Platt DM. Little evidence of a role for the α1GABAA subunit-containing receptor in a rhesus monkey model of alcohol drinking. Alcohol Clin Exp Res 2014; 38:1108-17. [PMID: 24330519 PMCID: PMC3984357 DOI: 10.1111/acer.12320] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 10/04/2013] [Indexed: 01/13/2023]
Abstract
BACKGROUND Alcohol potentiates GABAergic neurotransmission via action at the GABAA receptor. α1 subunit-containing GABAA receptors have been implicated as mediators, in part, of the behavioral and abuse-related effects of alcohol in rodents. METHODS We systematically investigated the effects of 1 α1-preferring benzodiazepine agonist, zolpidem, and 2 antagonists, β-carboline-3-carboxylate-tert-butyl ester (βCCT) and 3-propoxy-β-carboline hydrochloride (3-PBC), on oral self-administration of alcohol (2% w/v) or sucrose solution and observable behavior in rhesus macaques. We compared these effects to those of the nonselective benzodiazepine agonist triazolam, antagonist flumazenil, and inverse agonist β-carboline carboxylate (βCCE). RESULTS Alcohol and sucrose solutions maintained reliable baseline drinking behavior across the study. The α1-preferring compounds did not affect intake, number of sipper extensions, or blood alcohol levels (BALs) at any of the doses tested. Zolpidem, βCCT, and 3-PBC increased latency to first sipper extension in animals self-administering alcohol, but not sucrose, solution. Triazolam exerted biphasic effects on alcohol-drinking behavior, increasing intake at low doses but decreasing BAL and increasing latency at higher doses. At doses higher than those effective in alcohol-drinking animals, triazolam increased sucrose intake and latency. Flumazenil nonsystematically increased number of extensions for alcohol but decreased BAL, with no effects on sucrose drinking. βCCE decreased sipper extensions for alcohol and increased latency for first sucrose sipper extension, but full dose-effect relationships could not be determined due to seizures at higher doses. CONCLUSIONS Alcohol-drinking animals appeared more sensitive to the effects of GABAergic compounds on drinking behavior. However, these results do not support a strong contribution of α1GABAA receptors to the reinforcing effects of alcohol in primates.
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Affiliation(s)
- Eileen K. Sawyer
- Harvard Medical School, New England Primate Research Center, Southborough, MA, USA
| | - Casey Moran
- Harvard Medical School, New England Primate Research Center, Southborough, MA, USA
| | - Madelynn H. Sirbu
- Harvard Medical School, New England Primate Research Center, Southborough, MA, USA
| | - Melissa Szafir
- Harvard Medical School, New England Primate Research Center, Southborough, MA, USA
| | - Michael Van Linn
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee WI
| | - Ojas Namjoshi
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee WI
| | | | - James M. Cook
- Department of Chemistry and Biochemistry, University of Wisconsin-Milwaukee, Milwaukee WI
| | - Donna M. Platt
- Harvard Medical School, New England Primate Research Center, Southborough, MA, USA
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Silveri MM. GABAergic contributions to alcohol responsivity during adolescence: insights from preclinical and clinical studies. Pharmacol Ther 2014; 143:197-216. [PMID: 24631274 DOI: 10.1016/j.pharmthera.2014.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 02/28/2014] [Indexed: 01/04/2023]
Abstract
There is a considerable body of literature demonstrating that adolescence is a unique age period, which includes rapid and dramatic maturation of behavioral, cognitive, hormonal and neurobiological systems. Most notably, adolescence is also a period of unique responsiveness to alcohol effects, with both hyposensitivity and hypersensitivity observed to the various effects of alcohol. Multiple neurotransmitter systems are undergoing fine-tuning during this critical period of brain development, including those that contribute to the rewarding effects of drugs of abuse. The role of developmental maturation of the γ-amino-butyric acid (GABA) system, however, has received less attention in contributing to age-specific alcohol sensitivities. This review integrates GABA findings from human magnetic resonance spectroscopy studies as they may translate to understanding adolescent-specific responsiveness to alcohol effects. Better understanding of the vulnerability of the GABA system both during adolescent development, and in psychiatric conditions that include alcohol dependence, could point to a putative mechanism, boosting brain GABA, that may have increased effectiveness for treating alcohol use disorders.
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Affiliation(s)
- Marisa M Silveri
- Neurodevelopmental Laboratory on Addictions and Mental Health, McLean Hospital, Belmont, MA, USA; Department of Psychiatry, Harvard Medical School, Boston, MA, USA.
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Blednov YA, Benavidez JM, Black M, Leiter CR, Osterndorff-Kahanek E, Johnson D, Borghese CM, Hanrahan JR, Johnston GAR, Chebib M, Harris RA. GABAA receptors containing ρ1 subunits contribute to in vivo effects of ethanol in mice. PLoS One 2014; 9:e85525. [PMID: 24454882 PMCID: PMC3894180 DOI: 10.1371/journal.pone.0085525] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/27/2013] [Indexed: 11/29/2022] Open
Abstract
GABAA receptors consisting of ρ1, ρ2, or ρ3 subunits in homo- or hetero-pentamers have been studied mainly in retina but are detected in many brain regions. Receptors formed from ρ1 are inhibited by low ethanol concentrations, and family-based association analyses have linked ρ subunit genes with alcohol dependence. We determined if genetic deletion of ρ1 in mice altered in vivo ethanol effects. Null mutant male mice showed reduced ethanol consumption and preference in a two-bottle choice test with no differences in preference for saccharin or quinine. Null mutant mice of both sexes demonstrated longer duration of ethanol-induced loss of righting reflex (LORR), and males were more sensitive to ethanol-induced motor sedation. In contrast, ρ1 null mice showed faster recovery from acute motor incoordination produced by ethanol. Null mutant females were less sensitive to ethanol-induced development of conditioned taste aversion. Measurement of mRNA levels in cerebellum showed that deletion of ρ1 did not change expression of ρ2, α2, or α6 GABAA receptor subunits. (S)-4-amino-cyclopent-1-enyl butylphosphinic acid (“ρ1” antagonist), when administered to wild type mice, mimicked the changes that ethanol induced in ρ1 null mice (LORR and rotarod tests), but the ρ1 antagonist did not produce these effects in ρ1 null mice. In contrast, (R)-4-amino-cyclopent-1-enyl butylphosphinic acid (“ρ2” antagonist) did not change ethanol actions in wild type but produced effects in mice lacking ρ1 that were opposite of the effects of deleting (or inhibiting) ρ1. These results suggest that ρ1 has a predominant role in two in vivo effects of ethanol, and a role for ρ2 may be revealed when ρ1 is deleted. We also found that ethanol produces similar inhibition of function of recombinant ρ1 and ρ2 receptors. These data indicate that ethanol action on GABAA receptors containing ρ1/ρ2 subunits may be important for specific effects of ethanol in vivo.
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Affiliation(s)
- Yuri A. Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Jillian M. Benavidez
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Mendy Black
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Courtney R. Leiter
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Elizabeth Osterndorff-Kahanek
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - David Johnson
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Cecilia M. Borghese
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
| | - Jane R. Hanrahan
- Faculty of Pharmacy, The University of Sydney, Sydney NSW, Australia
| | | | - Mary Chebib
- Faculty of Pharmacy, The University of Sydney, Sydney NSW, Australia
| | - R. Adron Harris
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, Austin, Texas, United States of America
- * E-mail:
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Abstract
Addictions are prevalent psychiatric disorders that confer remarkable personal and social burden. Despite substantial evidence for their moderate, yet robust, heritability (approx. 50%), specific genetic mechanisms underlying their development and maintenance remain unclear. The goal of this selective review is to highlight progress in unveiling the genetic underpinnings of addiction. First, we revisit the basis for heritable variation in addiction before reviewing the most replicable candidate gene findings and emerging signals from genomewide association studies for alcohol, nicotine and cannabis addictions. Second, we survey the modest but growing field of neurogenetics examining how genetic variation influences corticostriatal structure, function, and connectivity to identify neural mechanisms that may underlie associations between genetic variation and addiction. Third, we outline how extant genomic findings are being used to develop and refine pharmacotherapies. Finally, as sample sizes for genetically informed studies of addiction approach critical mass, we posit five exciting possibilities that may propel further discovery (improved phenotyping, rare variant discovery, gene-environment interplay, epigenetics, and novel neuroimaging designs).
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Rüedi-Bettschen D, Rowlett JK, Rallapalli S, Clayton T, Cook JM, Platt DM. Modulation of α5 subunit-containing GABAA receptors alters alcohol drinking by rhesus monkeys. Alcohol Clin Exp Res 2013; 37:624-34. [PMID: 23126673 PMCID: PMC3951841 DOI: 10.1111/acer.12018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Accepted: 08/22/2012] [Indexed: 11/28/2022]
Abstract
BACKGROUND Alcohol's ability to potentiate the activity of γ-aminobutyric acid (GABA) at GABAA receptors has been implicated as a key mechanism underlying the behavioral effects of alcohol. The complex molecular biology of these receptors raises the possibility that particular receptor subtypes may play unique roles in alcohol's abuse-related effects and that subtype-selective ligands with therapeutic specificity against alcohol might be developed. This study evaluated the capacity of α5GABAA receptor ligands to alter selectively the reinforcing effects of alcohol. METHODS Two groups of rhesus monkeys were trained to orally self-administer alcohol or sucrose under fixed-ratio schedules and limited daily access conditions. In addition, following daily self-administration sessions, the behavior of each monkey was scored for both species-typical and drug-induced behaviors. RESULTS Concentrations of 1 to 6% alcohol maintained self-administration above water levels, engendered pharmacologically relevant blood alcohol levels ranging from 90 to 160 mg/dl, and produced changes in behavior typical of alcohol intoxication. Concentrations of 0.3 to 3% sucrose also reliably maintained self-administration. The α5GABAA receptor agonist QH-ii-066 enhanced and the α5GABAA receptor inverse agonist L-655,708 inhibited alcohol, but not sucrose drinking. The changes in alcohol drinking could be reversed with the α5GABAA receptor antagonist XLi-093. However, L-655,708 increased yawning in both alcohol and sucrose drinkers, possibly indicative of an anxiogenic effect. CONCLUSIONS These findings suggest a prominent and specific role for α5GABAA receptor mechanisms in the reinforcing effects of alcohol. Moreover, these results suggest that α5GABAA receptors may represent a novel pharmacological target for the development of medications to reduce drinking. Of ligands modulating this receptor, α5GABAA receptor inverse agonists may hold the most promise as alcohol pharmacotherapies.
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Behavioral characteristics of ubiquitin-specific peptidase 46-deficient mice. PLoS One 2013; 8:e58566. [PMID: 23472206 PMCID: PMC3589359 DOI: 10.1371/journal.pone.0058566] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Accepted: 02/05/2013] [Indexed: 11/19/2022] Open
Abstract
We have previously identified Usp46, which encodes for ubiquitin-specific peptidase 46, as a quantitative trait gene affecting the immobility time of mice in the tail suspension test (TST) and forced swimming test. The mutation that we identified was a 3-bp deletion coding for lysine (Lys 92), and mice with this mutation (MT mice), as well as Usp46 KO mice exhibited shorter TST immobility times. Behavioral pharmacology suggests that the gamma aminobutyric acid A (GABAA) receptor is involved in regulating TST immobility time. In order to understand how far Usp46 controls behavioral phenotypes, which could be related to mental disorders in humans, we subjected Usp46 MT and KO mice to multiple behavioral tests, including the open field test, ethanol preference test, ethanol-induced loss of righting reflex test, sucrose preference test, novelty-suppressed feeding test, marble burying test, and novel object recognition test. Although behavioral phenotypes of the Usp46 MT and KO mice were not always identical, deficiency of Usp46 significantly affected performance in all these tests. In the open field test, activity levels were lower in Usp46 KO mice than wild type (WT) or MT mice. Both MT and KO mice showed lower ethanol preference and shorter recovery times after ethanol administration. Compared to WT mice, Usp46 MT and KO mice exhibited decreased sucrose preference, took longer latency periods to bite pellets, and buried more marbles in the sucrose preference test, novelty-suppressed feeding test, and marble burying test, respectively. In the novel object recognition test, neither MT nor KO mice showed an increase in exploration of a new object 24 hours after training. These findings indicate that Usp46 regulates a wide range of behavioral phenotypes that might be related to human mental disorders and provides insight into the function of USP46 deubiquitinating enzyme in the neural system.
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Zarrindast MR, Mashayekhi M, Rezayof A, Ahmadi S. β-Adrenoceptors in the dorsal hippocampus are involved in ethanol-induced state-dependent retrieval in mice. Neurobiol Learn Mem 2013; 100:12-7. [DOI: 10.1016/j.nlm.2012.11.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Revised: 11/28/2012] [Accepted: 11/28/2012] [Indexed: 11/27/2022]
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Blednov YA, Benavidez JM, Black M, Chandra D, Homanics GE, Rudolph U, Harris RA. Linking GABA(A) receptor subunits to alcohol-induced conditioned taste aversion and recovery from acute alcohol intoxication. Neuropharmacology 2012; 67:46-56. [PMID: 23147414 DOI: 10.1016/j.neuropharm.2012.10.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Revised: 10/12/2012] [Accepted: 10/28/2012] [Indexed: 10/27/2022]
Abstract
GABA type A receptors (GABA(A)-R) are important for ethanol actions and it is of interest to link individual subunits with specific ethanol behaviors. We studied null mutant mice for six different GABA(A)-R subunits (α1, α2, α3, α4, α5 and δ). Only mice lacking the α2 subunit showed reduction of conditioned taste aversion (CTA) to ethanol. These results are in agreement with data from knock-in mice with mutation of the ethanol-sensitive site in the α2-subunit (Blednov et al., 2011). All together, they indicate that aversive property of ethanol is dependent on ethanol action on α2-containing GABA(A)-R. Deletion of the α2-subunit led to faster recovery whereas absence of the α3-subunit slowed recovery from ethanol-induced incoordination (rotarod). Deletion of the other four subunits did not affect this behavior. Similar changes in this behavior for the α2 and α3 null mutants were found for flurazepam motor incoordination. However, no differences in recovery were found in motor-incoordinating effects of an α1-selective modulator (zolpidem) or an α4-selective agonist (gaboxadol). Therefore, recovery of rotarod incoordination is under control of two GABA(A)-R subunits: α2 and α3. For motor activity, α3 null mice demonstrated higher activation by ethanol (1 g/kg) whereas both α2 (-/-) and α3 (-/Y) knockout mice were less sensitive to ethanol-induced reduction of motor activity (1.5 g/kg). These studies demonstrate that the effects of ethanol at GABAergic synapses containing α2 subunit are important for specific behavioral effects of ethanol which may be relevant to the genetic linkage of the α2 subunit with human alcoholism.
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Affiliation(s)
- Y A Blednov
- Waggoner Center for Alcohol and Addiction Research, The University of Texas at Austin, 1 University Station, A4800, Austin, TX 78712, USA.
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45
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Heistek TS, Ruiperez-Alonso M, Timmerman AJ, Brussaard AB, Mansvelder HD. α2-containing GABAA receptors expressed in hippocampal region CA3 control fast network oscillations. J Physiol 2012; 591:845-58. [PMID: 23109109 DOI: 10.1113/jphysiol.2012.243725] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
GABA(A) receptors are critically involved in hippocampal oscillations. GABA(A) receptor α1 and α2 subunits are differentially expressed throughout the hippocampal circuitry and thereby may have distinct contributions to oscillations. It is unknown which GABA(A) receptor α subunit controls hippocampal oscillations and where these receptors are expressed. To address these questions we used transgenic mice expressing GABA(A) receptor α1 and/or α2 subunits with point mutations (H101R) that render these receptors insensitive to allosteric modulation at the benzodiazepine binding site, and tested how increased or decreased function of α subunits affects hippocampal oscillations. Positive allosteric modulation by zolpidem prolonged decay kinetics of hippocampal GABAergic synaptic transmission and reduced the frequency of cholinergically induced oscillations. Allosteric modulation of GABAergic receptors in CA3 altered oscillation frequency in CA1, while modulation of GABA receptors in CA1 did not affect oscillations. In mice having a point mutation (H101R) at the GABA(A) receptor α2 subunit, zolpidem effects on cholinergically induced oscillations were strongly reduced compared to wild-type animals, while zolpidem modulation was still present in mice with the H101R mutation at the α1 subunit. Furthermore, genetic knockout of α2 subunits strongly reduced oscillations, whereas knockout of α1 subunits had no effect. Allosteric modulation of GABAergic receptors was strongly reduced in unitary connections between fast spiking interneurons and pyramidal neurons in CA3 of α2H101R mice, but not of α1H101R mice, suggesting that fast spiking interneuron to pyramidal neuron synapses in CA3 contain α2 subunits. These findings suggest that α2-containing GABA(A) receptors expressed in the CA3 region provide the inhibition that controls hippocampal rhythm during cholinergically induced oscillations.
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Affiliation(s)
- Tim S Heistek
- Department of Integrative Neurophysiology, CNCR, Neuroscience Campus Amsterdam, VU University, Amsterdam, The Netherlands
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46
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Dixon CI, Walker SE, King SL, Stephens DN. Deletion of the gabra2 gene results in hypersensitivity to the acute effects of ethanol but does not alter ethanol self administration. PLoS One 2012; 7:e47135. [PMID: 23115637 PMCID: PMC3480382 DOI: 10.1371/journal.pone.0047135] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 09/10/2012] [Indexed: 12/04/2022] Open
Abstract
Human genetic studies have suggested that polymorphisms of the GABRA2 gene encoding the GABAA α2-subunit are associated with ethanol dependence. Variations in this gene also convey sensitivity to the subjective effects of ethanol, indicating a role in mediating ethanol-related behaviours. We therefore investigated the consequences of deleting the α2-subunit on the ataxic and rewarding properties of ethanol in mice. Ataxic and sedative effects of ethanol were explored in GABAA α2-subunit wildtype (WT) and knockout (KO) mice using a Rotarod apparatus, wire hang and the duration of loss of righting reflex. Following training, KO mice showed shorter latencies to fall than WT littermates under ethanol (2 g/kg i.p.) in both Rotarod and wire hang tests. After administration of ethanol (3.5 g/kg i.p.), KO mice took longer to regain the righting reflex than WT mice. To ensure the acute effects are not due to the gabra2 deletion affecting pharmacokinetics, blood ethanol concentrations were measured at 20 minute intervals after acute administration (2 g/kg i.p.), and did not differ between genotypes. To investigate ethanol’s rewarding properties, WT and KO mice were trained to lever press to receive increasing concentrations of ethanol on an FR4 schedule of reinforcement. Both WT and KO mice self-administered ethanol at similar rates, with no differences in the numbers of reinforcers earned. These data indicate a protective role for α2-subunits, against the acute sedative and ataxic effects of ethanol. However, no change was observed in ethanol self administration, suggesting the rewarding effects of ethanol remain unchanged.
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Affiliation(s)
- Claire I. Dixon
- School of Psychology, University of Sussex, Brighton, United Kingdom
| | - Sophie E. Walker
- School of Psychology, University of Sussex, Brighton, United Kingdom
| | - Sarah L. King
- School of Psychology, University of Sussex, Brighton, United Kingdom
| | - David N. Stephens
- School of Psychology, University of Sussex, Brighton, United Kingdom
- * E-mail:
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47
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Blednov YA, Mayfield RD, Belknap J, Harris RA. Behavioral actions of alcohol: phenotypic relations from multivariate analysis of mutant mouse data. GENES BRAIN AND BEHAVIOR 2012; 11:424-35. [PMID: 22405477 DOI: 10.1111/j.1601-183x.2012.00780.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Behavioral studies on genetically diverse mice have proven powerful for determining relationships between phenotypes and have been widely used in alcohol research. Most of these studies rely on naturally occurring genetic polymorphisms among inbred strains and selected lines. Another approach is to introduce variation by engineering single-gene mutations in mice. We have tested 37 different mutant mice and their wild-type controls for a variety (31) of behaviors and have mined this data set by K-means clustering and analysis of correlations. We found a correlation between a stress-related response (activity in a novel environment) and alcohol consumption and preference for saccharin. We confirmed several relationships detected in earlier genetic studies, including positive correlation of alcohol consumption with saccharin consumption and negative correlations with conditioned taste aversion and alcohol withdrawal severity. Introduction of single-gene mutations either eliminated or greatly diminished these correlations. The three tests of alcohol consumption used (continuous two-bottle choice and two limited access tests: drinking in the dark and sustained high alcohol consumption) share a relationship with saccharin consumption, but differ from each other in their correlation networks. We suggest that alcohol consumption is controlled by multiple physiological systems where single-gene mutations can disrupt the networks of such systems.
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Affiliation(s)
- Y A Blednov
- Waggoner Center for Alcohol and Addiction Research, Section on Neurobiology, Institute for Neuroscience, Institute for Cell and Molecular Biology, University of Texas at Austin, TX 78712, USA
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48
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Abstract
Alcohol use disorders (AUDs) constitute the most common form of substance abuse. The development of AUDs involves repeated alcohol use leading to tolerance, alcohol withdrawal syndrome, and physical and psychological dependence, with loss of ability to control excessive drinking. Currently there is no effective therapeutic agent for AUDs without major side effects. Dihydromyricetin (DHM; 1 mg/kg, i.p. injection), a flavonoid component of herbal medicines, counteracted acute alcohol (EtOH) intoxication, and also withdrawal signs in rats including tolerance, increased anxiety, and seizure susceptibility; DHM greatly reduced EtOH consumption in an intermittent voluntary EtOH intake paradigm in rats. GABA(A) receptors (GABA(A)Rs) are major targets of acute and chronic EtOH actions on the brain. At the cellular levels, DHM (1 μM) antagonized both acute EtOH-induced potentiation of GABA(A)Rs and EtOH exposure/withdrawal-induced GABA(A)R plasticity, including alterations in responsiveness of extrasynaptic and postsynaptic GABA(A)Rs to acute EtOH and, most importantly, increases in GABA(A)R α4 subunit expression in hippocampus and cultured neurons. DHM anti-alcohol effects on both behavior and CNS neurons were antagonized by flumazenil (10 mg/kg in vivo; 10 μM in vitro), the benzodiazepine (BZ) antagonist. DHM competitively inhibited BZ-site [(3)H]flunitrazepam binding (IC(50), 4.36 μM), suggesting DHM interaction with EtOH involves the BZ sites on GABA(A)Rs. In summary, we determined DHM anti-alcoholic effects on animal models and determined a major molecular target and cellular mechanism of DHM for counteracting alcohol intoxication and dependence. We demonstrated pharmacological properties of DHM consistent with those expected to underlie successful medical treatment of AUDs; therefore DHM is a therapeutic candidate.
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49
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Morozova TV, Goldman D, Mackay TFC, Anholt RRH. The genetic basis of alcoholism: multiple phenotypes, many genes, complex networks. Genome Biol 2012; 13:239. [PMID: 22348705 PMCID: PMC3334563 DOI: 10.1186/gb-2012-13-2-239] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2011] [Accepted: 02/09/2012] [Indexed: 12/02/2022] Open
Abstract
Alcoholism is a significant public health problem. A picture of the genetic architecture underlying alcohol-related phenotypes is emerging from genome-wide association studies and work on genetically tractable model organisms.
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Affiliation(s)
- Tatiana V Morozova
- Department of Biology, Box 7617, North Carolina State University, Raleigh, NC 27695, USA
- WM Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA
| | - David Goldman
- National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA
| | - Trudy FC Mackay
- WM Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA
- Department of Genetics, North Carolina State University, Raleigh, NC 27695, USA
| | - Robert RH Anholt
- Department of Biology, Box 7617, North Carolina State University, Raleigh, NC 27695, USA
- WM Keck Center for Behavioral Biology, North Carolina State University, Raleigh, NC 27695, USA
- Department of Genetics, North Carolina State University, Raleigh, NC 27695, USA
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50
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Lingford-Hughes A, Reid AG, Myers J, Feeney A, Hammers A, Taylor LG, Rosso L, Turkheimer F, Brooks DJ, Grasby P, Nutt DJ. A [11C]Ro15 4513 PET study suggests that alcohol dependence in man is associated with reduced α5 benzodiazepine receptors in limbic regions. J Psychopharmacol 2012; 26:273-81. [PMID: 20870689 DOI: 10.1177/0269881110379509] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Preclinical evidence suggests the α5 subtype of the GABA-benzodiazepine receptor is involved in some of the actions of alcohol and in memory. The positron emission tomography (PET) tracer, [(11)C]Ro15 4513 shows relative selectivity in labelling the α5 subtype over the other GABA-benzodiazepine receptor subtypes in limbic regions of the brain. We used this tracer to investigate the distribution of α5 subtype availability in human alcohol dependence and its relationship to clinical variables. Abstinent (>6 weeks) alcohol-dependent men and healthy male controls underwent an [(11)C]Ro15 4513 PET scan. We report [(11)C]Ro15 4513 brain uptake for 8 alcohol-dependent men and 11 healthy controls. We found a significant reduction in [(11)C]Ro15 4513 binding in the nucleus accumbens, parahippocampal gyri, right hippocampus and amygdala in the alcohol-dependent compared with the healthy control group. Levels of [(11)C]Ro15 4513 binding in both hippocampi were significantly and positively associated with performance on a delayed verbal memory task in the alcohol-dependent but not the control group. We speculate that the reduced limbic [(11)C]Ro15 4513 binding seen here results from the effects of alcohol, though we cannot currently distinguish whether they are compensatory in nature or evidence of brain toxicity.
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Affiliation(s)
- Anne Lingford-Hughes
- Psychopharmacology Unit, Dorothy Hodgkin Building, University of Bristol, Bristol, UK.
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