The anxiolytic effect of acute ethanol or diazepam exposure is unaltered in μ-opioid receptor knockout mice

Abstract Previous researchers demonstrate an opioidergic involvement in the anxiolytic and rewarding actions of ethanol and diazepam. Therefore, to further characterize the role of the opioid system in the anxiolytic action of ethanol and diazepam, normal (C57BL/6J), hybrid (B6129F1) and μ-opioid receptor knockout mice were given i.p. ethanol (0, 1.0 or 1.6 g/kg) or diazepam (1.5 mg/kg). The anxiolytic properties of these agents were then tested in the elevated plus-maze. Additional ethanol-treated μ-opioid receptor knockout mice (1 g/kg) were pretreated with the κ-opioid receptor antagonist nor-BNI (0 or 3 mg/kg) to assess the involvement of κ-opioid activity in ethanol’s anxiolytic actions. The anxiolytic action of ethanol and diazepam in the μ-opioid receptor knockout mouse did not differ from the effects obtained in normal mice and pretreatment with nor-BNI did not significantly attenuate ethanol’s actions in μ-opioid receptor knockout mice. Thus, the anxiolytic actions of ethanol and diazepam appear to be independent of opioid system activity in the μ-opioid receptor knockout mouse.