Alteration of ethanol-induced changes in locomotor activity by adrenergic blockers in mice.

The effects of various doses of ethanol (ETOH) on spontaneous locomotor activity (SLMA) in mice were measured using photocell activity chambers. Of the 4 i.p. doses injected, the 2 lowest doses (0.5 and 1.0 g/kg) stimulated SLMA, the next higher dose (2.0 g/kg) produced a biphasic effect of depression followed by stimulation, and the highest dose (4.0 g/kg) depressed SLMA. The mechanism of the biphasic effect of the 2.0 g/kg dose was studied in tests with central catecholamine antagonists at various doses 30 min before ETOH. Doses of 5, 10, and 20 mg/kg of propranolol, a beta-receptor blocker, significantly antagonized the depressant effect of ETOH but had no influence on the stimulant effect. High doses (10 and 20 mg/kg) of phentolamine, an alpha-receptor blocker, significantly antagonized the stimulant phase of ETOH action but had no significant effect on the depressant phase. All doses (0.062-0.250 mg/kg) of spiroperidol, a dopaminergic blocking drug, significantly enhanced the SLMA depression produced by ETOH. These results indicate that the SLMA-depressant effect of ETOH may be mediated by central "beta-type" receptors, that the SLMA-stimulant effect of ETOH may be mediated by central "alpha-type" receptors, and that at least part of ETOH's action may be due to dopaminergic mechanisms.