Effects of MCH and a MCH1-receptor antagonist on (palatable) food and water intake

Melanin concentrating hormone (MCH) is a regulator of ingestive behavior, but several issues regarding its effects on specific components of ingestive behavior remain to be elucidated. Therefore, we injected, in the 3rd ventricle of male Wistar rats, saline, MCH (5 μg), MCH (5 μg) together with a MCH1-R antagonist (A, 10 μg) and the antagonist alone (A, 10 μg). Our results show that (1) central administration of MCH stimulates food intake (lab chow and medium high fat diet) and this can be blocked by a MCH1-R antagonist; (2) the MCH-induced increase in food intake is mediated through increased meal number, meal duration and meal size; (3) the MCH1-R antagonist is able to significantly reduce the intake of a highly palatable food (condensed sweet milk) and is more effective in blocking MCH-induced food intake when rats are fed a palatable medium high fat food; and (4) MCH stimulated water intake independently from and disproportionately to food intake. In conclusion, our results point to an involvement of endogenous MCH in the enhanced intake of palatable food. Furthermore, they confirm that MCH stimulates not only food intake but also water intake.