Central ghrelin induces feeding driven by energy needs not by reward.

Centrally administered ghrelin, the endogenous agonist of the growth hormone secretegogue receptor, powerfully stimulates food intake. Although the orexigenic action of this peptide has been well established, it remains unclear whether ghrelin-induced hyperphagia is driven by energy needs or by reward. In our study ghrelin was injected into the lateral cerebral ventricle or the hypothalamic paraventricular nucleus of rats given a choice between a palatable yet calorie-dilute sucrose solution and a calorically dense chow. As a result of intraventricular and hypothalamic paraventricular ghrelin injections, animals increased intake of chow but not sucrose. When the sucrose solution was offered as the only source of calories, rats treated with ghrelin infused in the ventricle and site-specifically increased sucrose consumption. These results suggest that the primary effect of ghrelin is to stimulate food intake to satisfy energy needs.