We have shown that ethanol dependence is associated with a reduction in GABAA receptor-mediated chloride channel function that may contribute to the development of physical dependence upon ethanol. The mechanism of these functional effects does not appear to involve a reduction in the number of GABA receptor-gated chloride channels. Prolonged ethanol exposure selectively and differentially alters the expression of several GABAA receptor subunit mRNAs and polypeptides in cortex and cerebellum. We have proposed that alterations in GABAA receptor subunit composition may be an important mechanism that underlies the reduction in GABAA receptor function and the development of dependence upon ethanol.
Our first aim i s to determine if chronic ethanol administration alters the subunit assembly of GABAA receptors using a combination of quantitative RT-PCR analysis of mRNA levels, Western blot analysis of polypeptide levels and immunoprecipitation studies with selective antibodies. Nuclear run-off experiments will be conducted to determine if changes in gene expression can be attributed to alterations in transcription rates. The next aim is to study the effects of chronic ethanol administration on GABAA receptor subunit expression in various brain regions where GABAA receptors differ in their sensitivity to ethanol. Studies of GABAA receptor expression at the cellular level are proposed using immunobinding assays on rat brain tissue sections. Our third goal is to investigate whether genetic differences in ethanol withdrawal seizure sensitivity are correlated with an alteration in a) the expression of GABAA receptor subunits in ethanol-naive mice or b) the effect of chronic ethanol administration on GABAA receptor subunit expression. Differences in GABAA receptor expression between the selected lines will then be subjected to genetic analysis to determine if the changes segregate with withdrawal seizure sensitivity. Our final goal is to investigate whether ethanol-induced alterations in GABAA receptor subunit expression are responsible for alterations in GABAA receptor function and CNS excitability. We plan to use selective antisense oligonucleotides to determine whether specific alterations in GABAA receptor expression in vivo are associated with the same alterations in GABAA receptor function and behavioral sensitivity that are observed with ethanol dependence. Future studies will address the same question in recombinant expression systems where the receptor subunit composition can be more precisely controlled. The results of these studies should have important implications for our understanding of the neurobiology of ethanol dependence and withdrawal.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
5R01AA009013-06
Application #
2732438
Study Section
Special Emphasis Panel (ZRG4-ALTX-3)
Project Start
1991-09-27
Project End
2001-06-30
Budget Start
1998-07-01
Budget End
1999-06-30
Support Year
6
Fiscal Year
1998
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Psychology
Type
Schools of Medicine
DUNS #
078861598
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Kralic, Jason E; Sidler, Corinne; Parpan, Franziska et al. (2006) Compensatory alteration of inhibitory synaptic circuits in cerebellum and thalamus of gamma-aminobutyric acid type A receptor alpha1 subunit knockout mice. J Comp Neurol 495:408-21
Kralic, Jason E; Criswell, Hugh E; Osterman, Jessica L et al. (2005) Genetic essential tremor in gamma-aminobutyric acidA receptor alpha1 subunit knockout mice. J Clin Invest 115:774-9
Kumar, Sandeep; Fleming, Rebekah L; Morrow, A Leslie (2004) Ethanol regulation of gamma-aminobutyric acid A receptors: genomic and nongenomic mechanisms. Pharmacol Ther 101:211-26
Kralic, J E; Wheeler, M; Renzi, K et al. (2003) Deletion of GABAA receptor alpha 1 subunit-containing receptors alters responses to ethanol and other anesthetics. J Pharmacol Exp Ther 305:600-7
Overstreet, David H; Kralic, Jason E; Morrow, A Leslie et al. (2003) NPI-031G (puerarin) reduces anxiogenic effects of alcohol withdrawal or benzodiazepine inverse or 5-HT2C agonists. Pharmacol Biochem Behav 75:619-25
Kumar, S; Kralic, J E; O'Buckley, T K et al. (2003) Chronic ethanol consumption enhances internalization of alpha1 subunit-containing GABAA receptors in cerebral cortex. J Neurochem 86:700-8
Kumar, Sandeep; Sieghart, Werner; Morrow, A Leslie (2002) Association of protein kinase C with GABA(A) receptors containing alpha1 and alpha4 subunits in the cerebral cortex: selective effects of chronic ethanol consumption. J Neurochem 82:110-7
Kralic, J E; Korpi, E R; O'Buckley, T K et al. (2002) Molecular and pharmacological characterization of GABA(A) receptor alpha1 subunit knockout mice. J Pharmacol Exp Ther 302:1037-45
Grobin, A C; Matthews, D B; Montoya, D et al. (2001) Age-related differences in neurosteroid potentiation of muscimol-stimulated 36Cl(-) flux following chronic ethanol treatment. Neuroscience 105:547-52
Papadeas, S; Grobin, A C; Morrow, A L (2001) Chronic ethanol consumption differentially alters GABA(A) receptor alpha1 and alpha4 subunit peptide expression and GABA(A) receptor-mediated 36 Cl(-) uptake in mesocorticolimbic regions of rat brain. Alcohol Clin Exp Res 25:1270-5

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