Neuropeptide Y Loses Its Orexigenic Effect in Rats with Lesions of the Hypothalamic Paraventricular Nucleus

Background. Both neuropeptide Y (NPY) and ghrelin can enhance the feeding behavior. The purpose of this study was to determine whether NPY and ghrelin are involved in hyperphagia and obesity induced by lesions of the hypothalamic paraventricular nucleus (PVN). Methods. Sham-operated control rats and rats subjected to bilateral electrolytic lesions of the PVN were administered NPY (5 μg/rat) by intracerebroventricular infusion or ghrelin (20 μg/kg) by intraperitoneal (i.p.) injection. Control rats were administered the appropriate vehicle by the same route as the drug. We measured the cumulative food intake (FI) for 2 h after infusion of NPY and for 4 h after ghrelin injection. Results. NPY significantly increased the cumulative FI in sham-operated rats. In PVN-lesioned rats, however, the cumulative FI at each time point (15 min, 30 min, 1 h, and 2 h) after NPY infusion was not significantly different from vehicle infusion, showing that NPY lost its orexigenic effect in PVN-lesioned rats. Following ghrelin...