Abstract:
While nicotine treatment to rodents causes a transient anorexia and persistent weight loss, withdrawal produces hyperphagia and weight gain. Herein, we test the hypothesis that endogenous anorectic peptide cocaine- and amphetamine-regulated transcript (CART) may be involved in these nicotine triggered physiological disturbances. In acute study, an anorectic effect of intraperitoneal nicotine was significantly potentiated by intracerebroventricular pre-treatment with CART at 2 and 4 h post-injection time-points. In chronic study, following an initial reduction, food intake, but not body weight, was progressively restored to normal. On the other hand, termination of chronic nicotine treatment resulted in significant hyperphagia and weight gain. These effects of nicotine were abolished if the rats were concomitantly treated with CART. An immunohistochemical profile of hypothalamic CART was studied following different nicotine treatment conditions. Acute nicotine treatment caused a significant increase above control in the CART-immunoreactive cells and fibers in the hypothalamic paraventricular (PVN) and fibers in the arcuate (ARC) nuclei. However, chronic nicotine administration had no effect on the CART-immunoreactivity in the PVN and ARC. While nicotine withdrawal reduced the population of CART-immunoreactive cells and fibers in the PVN, the immunoreactivity in the ARC fibers was increased. The results suggest that hypothalamic CART may process the acute, chronic and withdrawal effects of nicotine on feeding and body weight.