Peripheral serotonin administration selectively reduces fat intake in rats.

Recent research has led to the hypothesis that serotonergic mechanisms may be involved in both the control of energy intake and appetites for specific nutrients. Most of this research has focused on serotonin (5-HT) within the central nervous system. However, there is evidence which suggests that peripheral 5-HT also may be involved in the control of energy intake and nutrient selection. To further assess this suggestion, the effects of peripheral 5-HT administration on energy consumption and nutrient intakes were examined in adult male Sprague-Dawley rats given separate sources of protein, fat and carbohydrate. Administration of 5-HT (doses ranging from 2-6 mg/kg) led to significant dose-related decreases in total energy intake in both freely feeding and food-restricted rats. Examination of individual nutrient intakes revealed that following 5-HT, fat intake was more suppressed than either carbohydrate or protein intakes. Administration of the 5-HT antagonist, methysergide, blocked the suppressive effects of 5-HT on both total energy intake and fat intake. The present data support the proposal that peripheral serotonergic mechanisms play a role in ingestive behaviors.