Background. Tobacco smoking reduces appetite and body weight. Cessation of smoking leads to hyperphagia and weight gain. Food intake is a function of meal number (MN) and meal size (MZ) (ie, Food intake = MN x MZ). The effect of nicotine on these feeding components and their relationships to dopamine and serotonin in the lateral hyothalamic area (LHA) were determined. Methods. In Fischer-344 rats the effect of 7 days of systemic nicotine infusion on the feeding patterns was measured by rat eater meter and changes in serotonin (5HT) and dopamine (DA) in the LHA were measured by in vivo microdialysis. Results. Nicotine infusion caused hypophagia through a significant decrease in MN with a smaller decrease in MZ, resulting in a body weight reduction. 5HT and DA concomitantly increased in LHA. Stopping nicotine resulted in hyperphagia by a significant increase in MZ. Body weight normalized. 5HT and DA in LHA decreased after nicotine was stopped. Conclusion. Nicotine's hypophagic effect was associated with increased 5HT and DA in LHA, whereas hyperphagia after nicotine cessation was accompanied by decreased concentrations of the neurotransmitters. These findings suggest that nicotine affects appetite regulation, in part by modulation of LHA-DA and 5HT.
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