The effects of extended intravenous nicotine administration on body weight and meal patterns in male Sprague-Dawley rats.

RATIONALE: Increased appetite and weight gain after cessation is a deterrent for quitting smoking. Attempts to understand the mechanism for these effects using animals have been hampered by the difficulty or inconsistency of modeling the effects seen in humans.
OBJECTIVE: To examine the effects of extended daily access to intravenous nicotine, via programmed infusions, on body weight and meal patterns in rats.
METHODS: Intravenous (IV) nicotine infusions (0.06 mg/kg/inf) were administered noncontingently, every 30 min throughout the dark cycle and the last 3 h of the light cycle, to emulate self-administration. The effect of these infusions on food intake, meal patterns, and weight change were examined relative to a control group during treatment and in a post-nicotine phase.
RESULTS: Nicotine-treated rats gained half the weight that vehicle treated animals gained and ate approximately 20 % less food overall than vehicle-treated rats. Whereas a compensatory increase in meal frequency occurred during the dark period to account for smaller meals, no compensation was observed throughout the light period. In a post-nicotine phase, the nicotine group maintained a lower weight for 1 week and then gained weight back to control levels. The rate of weight gain post-cessation was faster in animals that had received nicotine compared to controls.
CONCLUSION: Compared to previous studies examining the effects of minipump or intraperitoneal injections of nicotine on food intake, the present study was able to detect previously unknown circadian differences in meal patterns which will be important in the development of smoking cessation and weight gain prevention drugs.