Effects of manipulations of peripheral serotonin on feeding and drinking in the rat

Rats injected peripherally with serotonin showed a dose dependent increase in water intake which was maximal at 2-hours. This effect, along with a dose dependent anorexia was also observed in animals eighteen hour food deprived overnight. In rats maintained on a 6-hour feeding schedule there was a significant anorectic effect of 5-HT that could be reversed by pretreatment with methysergide but not metergoline. However the hyperdipsia was not apparent in these animals due to prandial drinking by control animals. The optimal dose of 5-HT for producing an anorexic response produced only a transient conditioned taste aversion to a novel solution in a sensitive 2-bottle choice test. On the other hand a high dose of 5-HT, and 3 mg/kg fenfluramine produced sustained aversions. These results are discussed with regard to a possible peripheral role for 5-HT in the control of food intake.