γ-hydroxybutyric acid and diazepam antagonize a rapid increase in GABAA receptors α4 subunit mRNA abundance induced by ethanol withdrawal in cerebellar granule cells

Both benzodiazepines and gamma-hydroxybutyric acid (GHB) are used to treat alcohol withdrawal syndrome. The molecular basis for this therapeutic efficacy was investigated with primary cultures of rat cerebellar granule cells. Long-term exposure of these cells to ethanol (100 mM, 5 days) reduced the abundance of mRNAs encoding the gamma(2)L and gamma(2)S subunits of the GABA type A receptor (-32 and -23%, respectively) but failed to affect that of alpha(1), alpha(4), or alpha(6) subunit mRNAs. Subsequent ethanol withdrawal resulted in decreases in the amounts of alpha(1) (-29%), alpha(6) (-27%),. gamma(2)L (-64%), and gamma(2)S (-76%),subunit mRNAs that were maximal after 6 to 12 h. In contrast, 3 h after ethanol withdrawal, the abundance of the alpha(4) subunit mRNA was increased by 46%. Ethanol withdrawal did not affect neuronal morphology but reduced cellular metabolic activity. The increase in alpha(4) subunit was confirmed by functional studies showing a positive action of flumazenil in patch clamp recordings of GABA-stimulated currents after ethanol withdrawal. Diazepam (10 muM) or GHB (100 mM) prevented the increase in the amount of the alpha(4) subunit mRNA, the metabolic impairment, and the positive action of flumazenil induced by ethanol withdrawal but failed to restore the expression of the alpha(1) and gamma(2) subunits. The antagonism by GHB seems not to be mediated by a direct action at GABA(A)R because GHB failed to potentiate the effects of GABA or diazepam on Cl- currents mediated by GABA type A receptor.