Synergistic effects of serotonin and D-lys3- GHRP-6 on food intakes in food deprived male rats

Serotonin exerts an inhibitory effect on food intakes. D-Lys3 -GHRP-6 is a ghrelin receptor antagonist which inhibits fasting or ghrelin- induced food intake. In the present study, the effects of serotonin on food intakes were investigated in D-Lys 3 - GHRP-6- treated food-deprived male rats. Twenty food-deprived male rats in four groups (5 in each) received third cerebral ventricular injection of saline, 10µg serotonin, 20nmol D-Lys 3 -GHRP-6 or combination of D-Lys 3 -GHRP-6 and serotonin respectively.  Mean of one hour food intakes were measured. Data was analyzed by one-way analysis of variance (ANOVA) with post hoc Tukey’s test.  In all cases, P<0.05 was considered to be statistically significant. Serotonin, D-Lys 3 - GHRP-6 or combination of serotonin/D-Lys 3 - GHRP-6 decreased the mean food intakes significantly when compared to saline. A significant decrease was observed on mean food intakes between combination of D-Lys 3 -GHRP-6 and serotonin group and serotonin or D-Lys 3 - GHRP-6 groups. A significant decrease was not observed on food intakes between serotonin and D-Lys 3 - GHRP-6 groups. Serotonin and D-Lys 3 -GHRP-6 may exert synergistic inhibitory effects on food intake in rats. Decrease of the ghrelin pathway activity may have a role in mediating the inhibitory effects of serotonin on food intakes.