Effects of oral administration of nicotine on circadian rhythms of ambulatory activity and drinking in rats.

Effects of nicotine on circadian rhythms of ambulatory activity and drinking in male Wistar rats were examined. Nicotine was administered through the drinking water, and the daily doses of nicotine were adjusted to 0.5, 5 and 20 mg/kg/day. The treatment of nicotine induced a dose-dependent increase in ambulatory activity. On the other hand, fluid intake decreased at a dose of 20 mg/kg/day. Although the ambulatory activity and drinking were influenced by a long-term oral administration of nicotine, their circadian patterns, which were characteristic of nocturnal animals, were not altered.