Chronic treatment of male Wistar rats with ethanol by inhalation did not affect the binding of [(3)H]flunitrazepam, [(3)H]GABA or [(3)H]muscimol to extensively washed synaptic membranes. Neither the affinity (K(d)) nor the number of binding sites (Bmax) for these ligands was changed. However, GABA enhancement of [(3)H]flunitrazepam binding was significantly decreased by approx. 40% in ethanol-treated animals (172% compared to 215%). Acute treatment with ethanol did not produce changes in the binding of [(3)H]flunitrazepam or [(3)H]muscimol. These findings suggest that chronic ethanol treatment leads to uncoupling of the various receptor sites on the GABA-benzodiazepine receptor ionophore-complex in the brain.