Increased food intake and carbohydrate preference in the rat following treatment with the serotonin antagonist metergoline.

The effect on feeding of antagonism of the serotonergic system was studied. Intraperitoneal injection of one of 8 doses of the serotonin antagonist metergoline (MET) (0.06-1.5 mg.kg-1) given prior to a 3 h food deprivation produced a significant dose-related increase in intake of a standard laboratory diet throughout a 2 h measurement period. A 1 mg/kg dose of MET administered prior to one of 3 isocaloric powdered diets a medium carbohydrate, a high carbohydrate, and a non-carbohydrate diet - produced a significant increase in the intake by rats of all 3 diets in the first hour after food presentation. However, in the second hour MET continued to increase consumption of the high carbohydrate diet, whereas intakes of the medium carbohydrate and non-carbohydrate diets were no longer affected by MET treatment. These data suggest that the serotonergic system is a tonic inhibitor of food intake and of carbohydrate preference.