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 GABAAR because GHB failed to potentiate the effects of GABA or diazepam on Cl− currents mediated by GABA type A receptor.
Footnotes
-
This study was supported by Ministero dell'Istruzione dell'Universita e della Ricerca grant 2001055774.
- Abbreviations:
- GABAAR
- GABA type A receptors
- GHB
- γ-hydroxybutyric acid
- PCR
- polymerase chain reaction
- MBS
- modified Barth's solution
- ANOVA
- analysis of variance
- Received August 12, 2002.
- Accepted January 7, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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