Chronic Nicotine Infusion in Rats: Evidence for Some Noncholinergic Actions
Recently, we reported (Aceto et al., Pharmacologist, 27, 225, 1985) that nicotine di-l-tartrate given continuously by intraperitoneal infusion (Teiger, 190, 405, 1974) at a dose of 0.1 µg/kg/sec (base) markedly suppressed drinking during the first day of infusion. In addition, when nicotine was abruptly withdrawn six days later, water consumption increased dramatically during the first 24 hrs. We confirmed these results and conducted additional studies with mecamylamine, a nicotine antagonist. When given simultaneously with nicotine at doses of 0.01 and 0.05 µg/kg/sec, mecamylamine failed to block either the initial suppression of drinking or the rebound increase during withdrawal. The vehicle and mecamylamine controls had no significant effect on drinking. In addition, the rats receiving nicotine or nicotine plus mecamylamine did not gain as much body weight as the other subjects in the study. However, four days after abrupt withdrawal was initiated, body weight was in the same range as the vehicle controls. No behavioral signs were noted either during infusion or abrupt withdrawal. These results suggest that some of nicotine’s actions may not involve cholinergic mechanism.