Effects of chronic ethanol exposure on GABA(A) receptors may contribute to tolerance and dependence to alcohol. Ethanol treatment of mice and 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, Expression of bovine alpha(1), beta(1), and gamma(2L) GABA(A) receptor subunits genes in these cells is controlled by a dexamethasone-sensitive promoter, and this provides an excellent system to study the regulation by chronic ethanol treatment of receptors with a defined subunit composition. The actions of the GABA agonist muscimol on receptor function (Cl-36(-) uptake) were not affected by 100 mM ethanol treatment for 4 days, but the actions of flunitrazepam (1 mu M) were decreased in cells treated with ethanol, The functional coupling between benzodiazepine and GABA sites on the receptors was affected by chronic ethanol treatment in a manner consistent with results from mice, Ethanol treatments (50 or 100 mM) for 4 days did not affect the affinity (K-d) or receptor 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 gene promoters, is posttranscriptional and likely posttranslational.
GABA(A) RECEPTOR FUNCTION AND BINDING IN STABLY TRANSFECTED CELLS - CHRONIC ETHANOL TREATMENT
MASCIA MP;
1995
Abstract
Effects of chronic ethanol exposure on GABA(A) receptors may contribute to tolerance and dependence to alcohol. Ethanol treatment of mice and 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, Expression of bovine alpha(1), beta(1), and gamma(2L) GABA(A) receptor subunits genes in these cells is controlled by a dexamethasone-sensitive promoter, and this provides an excellent system to study the regulation by chronic ethanol treatment of receptors with a defined subunit composition. The actions of the GABA agonist muscimol on receptor function (Cl-36(-) uptake) were not affected by 100 mM ethanol treatment for 4 days, but the actions of flunitrazepam (1 mu M) were decreased in cells treated with ethanol, The functional coupling between benzodiazepine and GABA sites on the receptors was affected by chronic ethanol treatment in a manner consistent with results from mice, Ethanol treatments (50 or 100 mM) for 4 days did not affect the affinity (K-d) or receptor 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 gene promoters, is posttranscriptional and likely posttranslational.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
