Role of hypothalamic monoamines in nicotine-induced anorexia in menopausalrats

Background. Nicotine reduces body weight by reducing appetite. Estradiol mo dulates food intake. Menopause or ovariectomy (Ovx) increases food intake a nd body weight. Nicotine and estradiol individually influence hypothalamic dopamine (DA) and serotonin (5-HT), whose interaction influences food intak e and body weight. We investigated whether lower weight gain in menopausal smokers is mediated via changes in hypothalamic DA/5-HT. Methods. Ovx or sham-operated female rats had 2 microdialysis guide cannula s simultaneously implanted in ipsilateral ventromedial nucleus of hypothala mus (VMN) and contralateral lateral hypothalamic area (LHA). Rats were divi ded into 4 groups and received a continuous subcutaneous infusion of nicoti ne or saline Ovx and sham. DA and 5-HT in LHA and VMN were measured by in v ivo microdialysis. Results. Nicotine infusion decreased food intake and body weight in Ovx and sham groups. Increase in LHA-DA and VMN-5-HT in sham group occurred with n icotine, whereas an increase in VMN-DA in Ovx groups with and without nicot ine and VMN-5-HT in Ovx group with nicotine was observed. Conclusions. In the presence of estradiol (ovary intact sham-operated rats) , nicotine lowers food intake and body weight via increased LHA-DA and VMN- 5-HT In menopause (Ovx rats), nicotine lowers food intake and body weight o nly via increased VMN-DA and 5-HT Data show that lower weight gain is media ted via changes in hypothalamic monoamines, primarily via ventromedial hypo thalamus.