Some effects of nicotine on food and water intake in undeprived rats.

Undeprived rats were tested in their home cages for intake of water and powered food, starting 15 min after subcutaneous (s.c.) injection of (-)-nicotine bitartrate or 0.9% w/v NaCl solution (saline). In the first 2 h, nicotine (0-0.4 mg kg-1 base) markedly reduced water intake in a dose-related way, leaving food intake unchanged. Food and water intake up to 24 h after injection was unaffected. Rats (n = 6 per group) were then injected daily with nicotine (0.4 mg kg-1 base, s.c.) or saline for one month. Intermittent tests with saline (in place of nicotine) during this period did not reveal any signs of abstinence. A dose-response study similar to the first was then carried out, and little or no tolerance was found to the hypodipsic action of nicotine. Nicotine also reduced food intake, irrespective of chronic treatment. Subsequently, daily injections were discontinued, and spontaneous intake did not differ in rats previously maintained on nicotine, relative to control animals. Mecamylamine (0.3, 1.5 mg kg-1, s.c.) prevented nicotine-induced hypodipsia, whereas chlorisondamine (0.02, 0.1 mg kg-1 s.c.) was ineffective. Both ganglion blockers reduced food intake. Nicotine did not reduce drinking in rats preloaded with a hypertonic saline solution. It is suggested that nicotine reduces water intake in undeprived rats, probably by acting centrally. Since this action changes little with repeated testing, it may provide a useful index of one or more central actions of the drug.