Effects of Gabra2 Point Mutations on Alcohol Intake: Increased Binge-Like and Blunted Chronic Drinking by Mice
Corresponding Author
Emily L. Newman
Department of Psychology, Tufts University, Medford, Massachusetts
Reprint requests: Emily L. Newman, MS, Department of Psychology, Tufts University, 530 Boston Avenue, Medford, MA 02155; Tel.: 617-627-2792; Fax: 617-627-3939; E-mails: [email protected], or [email protected]Search for more papers by this authorGeorgia Gunner
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorPolly Huynh
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorDarrel Gachette
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorStephen J. Moss
Department of Neuroscience, Tufts University, Boston, Massachusetts
Search for more papers by this authorTrevor G. Smart
Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
Search for more papers by this authorUwe Rudolph
Laboratory of Genetic Neuropharmacology, McLean Hospital, Belmont, Massachusetts
Department of Psychiatry, Harvard Medical School, Boston, Massachusetts
Search for more papers by this authorJoseph F. DeBold
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorKlaus A. Miczek
Department of Psychology, Tufts University, Medford, Massachusetts
Department of Neuroscience, Tufts University, Boston, Massachusetts
Search for more papers by this authorCorresponding Author
Emily L. Newman
Department of Psychology, Tufts University, Medford, Massachusetts
Reprint requests: Emily L. Newman, MS, Department of Psychology, Tufts University, 530 Boston Avenue, Medford, MA 02155; Tel.: 617-627-2792; Fax: 617-627-3939; E-mails: [email protected], or [email protected]Search for more papers by this authorGeorgia Gunner
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorPolly Huynh
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorDarrel Gachette
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorStephen J. Moss
Department of Neuroscience, Tufts University, Boston, Massachusetts
Search for more papers by this authorTrevor G. Smart
Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
Search for more papers by this authorUwe Rudolph
Laboratory of Genetic Neuropharmacology, McLean Hospital, Belmont, Massachusetts
Department of Psychiatry, Harvard Medical School, Boston, Massachusetts
Search for more papers by this authorJoseph F. DeBold
Department of Psychology, Tufts University, Medford, Massachusetts
Search for more papers by this authorKlaus A. Miczek
Department of Psychology, Tufts University, Medford, Massachusetts
Department of Neuroscience, Tufts University, Boston, Massachusetts
Search for more papers by this authorAbstract
Background
Alcohol use disorders are associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABAA receptor α2-subunit in humans. Deficient GABAergic functioning is linked to impulse control disorders, intermittent explosive disorder, and to drug abuse and dependence, yet it remains unclear whether α2-containing GABAA receptor sensitivity to endogenous ligands is involved in excessive alcohol drinking.
Methods
Male wild-type (Wt) C57BL/6J and point-mutated mice rendered insensitive to GABAergic modulation by benzodiazepines (BZD; H101R), allopregnanolone (ALLO) or tetrahydrodeoxycorticosterone (THDOC; Q241M), or high concentrations of ethanol (EtOH) (S270H/L277A) at α2-containing GABAA receptors were assessed for their binge-like, moderate, or escalated chronic drinking using drinking in the dark, continuous access (CA) and intermittent access (IA) to alcohol protocols, respectively. Social approach by mutant and Wt mice in forced alcohol abstinence was compared to approach by EtOH-naïve controls. Social deficits in forced abstinence were treated with allopregnanolone (0, 3.0, 10.0 mg/kg, intraperitoneal [i.p.]) or midazolam (0, 0.56, 1.0 mg/kg, i.p.).
Results
Mice with BZD-insensitive α2-containing GABAA receptors (H101R) escalated their binge-like drinking. Mutants harboring the Q241M point substitution in Gabra2 showed blunted chronic intake in the CA and IA protocols. S270H/L277A mutants consumed excessive amounts of alcohol but, unlike wild-types, they did not show forced abstinence-induced social deficits.
Conclusions
These findings suggest a role for: (i) H101 in species-typical binge-like drinking, (ii) Q241 in escalated chronic drinking, and (iii) S270 and/or L277 in the development of forced abstinence-associated social deficits. Clinical findings report reduced BZD-binding sites in the cortex of dependent patients; the present findings suggest a specific role for BZD-sensitive α2-containing receptors. In addition, amino acid residue 241 in Gabra2 is necessary for positive modulation and activation of GABAA receptors by ALLO and THDOC; we postulate that neurosteroid action on α2-containing receptor may be necessary for escalated chronic EtOH intake.
Graphical Abstract
Alcohol dependence is associated with single-nucleotide polymorphisms in GABRA2, the gene encoding the GABAA receptor α2-subunit. Gabra2 point-mutated mice consumed alcohol in drinking-in-the-dark, continuous, or intermittent access to alcohol protocols. Compared to wild-types, α2(H101R) mice with benzodiazepine-insensitive α2-containing receptors (HR) escalated their binge-like intake and α2(Q241M) mutants with allopregnanolone- and THDOC-insensitive α2-containing receptors reduced their chronic drinking (QM). These findings suggest distinctive roles for select amino acids in the Gabra2 mouse gene in binge-like and chronic alcohol intake.
Supporting Information
| Filename | Description |
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| acer13215-sup-0001-FigS1-S7.pptxapplication/mspowerpoint, 322.5 KB |
Fig. S1. Each bar represents a separate cohort of mice comprised of EtOH-naïve or intermittent alcohol access (IAA) Wt, H101R, Q241M, and S270H/L277A mutant males. Fig. S2. Two doors, one on either site of the central chamber, are operated by pressurizing air piston systems attached to the top of each door. Fig. S3. EtOH intake (g/kg) intake by Wt and H101R (HR) point-mutants during the 4-hour binge on the last day of the DID protocol without concurrent access to water (A) or in an adapted 2BC DID protocol with concurrent access to water (B). Fig. S4. Wt and α2-subunit H101R, Q241M and S270H/L277A point-mutated males. Fig. S5. Daily 20% EtOH intake (g/kg) for the entire 16 weeks that Wt and mutant Gabra2 H101R (HR), Q241M (QM), and S270H/L277A (SH/LA) males received access to intermittent 20% EtOH access. Fig. S6. Time spent in the social approach zone (s) and distance traveled (cm) by EtOH-naïve Wt (A, C) and EtOH-naïve Q241M mutants (B, D) administered doses of MDZ (0.56 and 1.0 mg/kg) and ALLO (3.0 and 10.0 mg/kg). Fig. S7. Wt and mutant mice received 4 days of 2BC access to ascending concentrations of sucrose (10, 30, 100 mM; top) or quinine (0.1, 0.3 mM; bottom) solutions and water. |
| acer13215-sup-0002-Legends.docxWord document, 15.5 KB |
Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
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