Does the increase in locomotion induced by ethanol indicate its stimulant or anxiolytic properties?

The responses of mice to low doses of acutely and chronically administered ethanol (2.0 g/kg) and diazepam (2.0 mg/kg) were observed in the activity cages, the open field and the elevated plus-maze. After prolonged administration, ethanol significantly increased locomotion in the activity cages and the plus-maze. In the open field, an increase was only observed in the tests performed after 7 and 14 days of treatment. Ethanol increased the open-arm time in the plus-maze in all the tests, including after acute administration, suggesting an anxiolytic effect. Diazepam induced an anxiolytic effect after 14 days of daily injections but had no stimulant effect on locomotion. Moreover, after prolonged administration sensitization to the anxiolytic, but not to the stimulant effect, was observed. In short, the present paper's data support the hypothesis that the stimulant and anxiolytic effects of ethanol are probably being mediated by distinct mechanisms. Furthermore, these data support the hypothesis that drugs that lead to abusive use, such as ethanol, may act both as positive and negative reinforcement. (C) 2000 Elsevier Science Inc. All rights reserved.