Partial reversal of ethanol-induced reductions in exploration by two benzodiazepine antagonists (flumazenil and ZK 93426)

A series of experiments was performed to examine the effects of two benzodiazepine antagonists, flumazenil and ZK 93426, on the behavioral changes caused by ethanol (2 g/kg) in a holeboard test. The interaction between ethanol and low doses of diazepam (0.2 and 0.5 mg/kg) was also investigated. Both flumazenil and ZK 93426 reversed the reduction in exploration caused by ethanol, but tended to increase exploration when administered alone. In contrast, diazepam, which also increased exploration alone, tended to enhance the reduction in exploration caused by ethanol. Diazepam reduced the motor stimulant action of ethanol. The partial reversal by the two antagonists of the reduction in exploration caused by ethanol was not due to alterations in blood ethanol concentrations but may have resulted from their intrinsic exploration-increasing effects or an antagonism of an endogenous ligand for central benzodiazepine receptors.