Alcohol withdrawal is associated with affective-behavioral disturbances in both human alcoholics and in animal models. In general, these phenomena are potentiated by increased alcohol exposure duration and by prior withdrawal episodes. Previous studies have also reported locomotor hypoactivity during ethanol withdrawal in rats and mice, but only in novel test environments, not in the home-cage. In the present study, we examined the effects of withdrawal from chronic intermittent ethanol (CIE) vapor exposure on the level and circadian periodicity of wheel-running activity in C57BL/6J mice. CIE treatment resulted in reductions in wheel-running activity relative to plain-air controls that persisted for about one week after withdrawal. Analysis of circadian waveforms indicated that reduced activity occurred throughout the night phase, but that daily activity patterns were otherwise unaltered. CIE failed to alter free-running circadian period or phase in animals maintained under constant darkness. These results show that ethanol withdrawal can result in locomotor hypoactivity even in the habitual, home-cage environment, and suggest that withdrawal-related reductions in wheel-running activity may reflect the specific motivational significance of this behavior.

The effects of nimodipine, an L-type calcium channel antagonist, on nicotine-induced locomotor activity were investigated in drug-naive rats. Nicotine (0.4 mg/kg i.p.) produced significant increases in locomotion following acute administration. However, when rats were given injections of nimodipine (5, 10, or 20 mg/kg i.p.) 1 h prior to the test drug, nicotine-induced locomotor activity was altered. Nimodipine 5 mg did not significantly block locomotor activity produced by nicotine. In contrast, pretreatment with 10 and 20 mg nimodipine significantly blocked nicotine-induced locomotor activity. These findings clearly indicate that nicotine-induced locomotion is altered by nimodipine in a dose-dependent fashion. Results further suggest that the effect of nicotine on locomotion is calcium-dependent.