Behavioral interactions between ethanol and imidazodiazepines with high affinities for benzodiazepine receptors.

The intrinsic effects of two imidazodiazepines RO 15-3505 and RO 17-1812 on the behavior of mice in a holeboard test were investigated. The interactions of these two drugs with ethanol were also studied. RO 15-3505 (0.75-6.0 mg/kg) failed to significantly alter either exploratory head-dipping or locomotor activity when administered alone but doses of 0.75 and 1.5 mg/kg reversed the reduction in the number of head-dips caused by ethanol (2 g/kg) and partially reversed ethanol's locomotor stimulant action. In contrast, RO 17-1812 (0.75-6.0 mg/kg) increased locomotor activity when administered alone, and enhanced the reduction in exploration caused by ethanol. Neither RO 15-3505 nor RO 17-1812 altered blood alcohol concentrations suggesting a pharmacodynamic basis for these interactions. The results suggest that in the holeboard test the interactions of imidazodiazepines with ethanol are related to the nature of their interaction with benzodiazepine receptors, inverse agonists antagonising and agonists enhancing ethanol's effects on exploration.