Naloxone potentiates the effects of subeffective doses of anxiolytic agents in mice.

The ability of the opioid receptor antagonist naloxone to potentiate the effects of subeffective doses of chlordiazepoxide, diazepam and buspirone was evaluated in Swiss mice tested in an elevated plus maze. Diazepam (0.5 mg/kg), chlordiazepoxide (2.5 mg/kg) and buspirone (2 mg/kg) were ineffective per se but, when combined with naloxone (10 mg/kg), they increased the proportion of open arm entries as did higher doses of the anxiolytic agents (diazepam 1.5 mg/kg, chlordiazepoxide 5 mg/kg and buspirone 4 mg/kg). Naloxone alone (10 mg/kg) had no intrinsic effect. These data suggest that naloxone is able to potentiate the effects of anti-anxiety agents.