GABA(A) RECEPTOR FUNCTION AND BINDING IN STABLY TRANSFECTED CELLS - CHRONIC ETHANOL TREATMENT

Effects of chronic ethanol exposure on GABA(A) receptors may contribut e to tolerance and dependence to alcohol. Ethanol treatment of mice an d rats can produce alterations of GABA(A) receptor binding, function, and subunit mRNA and protein levels, We treated a cell line (PA3 cells ) that stably expresses GABA(A) receptors chronically with ethanol, Ex pression of bovine alpha(1), beta(1), and gamma(2L) GABA(A) receptor s ubunits genes in these cells is controlled by a dexamethasone-sensitiv e promoter, and this provides an excellent system to study the regulat ion by chronic ethanol treatment of receptors with a defined subunit c omposition. The actions of the GABA agonist muscimol on receptor funct ion (Cl-36(-) uptake) were not affected by 100 mM ethanol treatment fo r 4 days, but the actions of flunitrazepam (1 mu M) were decreased in cells treated with ethanol, The functional coupling between benzodiaze pine and GABA sites on the receptors was affected by chronic ethanol t reatment in a manner consistent with results from mice, Ethanol treatm ents (50 or 100 mM) for 4 days did not affect the affinity (K-d) or re ceptor density (B-max) of [H-3]flunitrazepam binding, or the levels of alpha(1) subunit mRNA, or alpha(1) or beta(1) subunit proteins. These results demonstrate that the regulation of the stably expressed GABA( A) receptors by chronic ethanol, in the absence of neuronal receptor g ene promoters, is posttranscriptional and likely posttranslational.