Abstract

Both benzodiazepines and γ-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 γ₂L and γ₂S subunits of the GABA type A receptor (−32 and −23%, respectively) but failed to affect that of α₁, α₄, or α₆ subunit mRNAs. Subsequent ethanol withdrawal resulted in decreases in the amounts of α₁ (−29%), α₆ (−27%), γ₂L (−64%), and γ₂S (−76%),subunit mRNAs that were maximal after 6 to 12 h. In contrast, 3 h after ethanol withdrawal, the abundance of the α₄ subunit mRNA was increased by 46%. Ethanol withdrawal did not affect neuronal morphology but reduced cellular metabolic activity. The increase in α₄ 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 μM) or GHB (100 mM) prevented the increase in the amount of the α₄ subunit mRNA, the metabolic impairment, and the positive action of flumazenil induced by ethanol withdrawal but failed to restore the expression of the α₁ and γ₂subunits. The antagonism by GHB seems not to be mediated by a direct action at GABA_AR because GHB failed to potentiate the effects of GABA or diazepam on Cl⁻ currents mediated by GABA type A receptor.