HORMONAL AND METABOLIC EFFECTS OF PARAVENTRICULAR HYPOTHALAMIC ADMINISTRATION OF NEUROPEPTIDE-Y DURING REST AND FEEDING

To investigate the role of neuropeptide Y (NPY) in the paraventricular nucleus of the hypothalamus (PVN) in the regulation of autonomic outf low, hormonal (plasma insulin and catecholamines), metabolic (blood gl ucose and plasma free fatty acids) and cardiovascular (heart rate and main arterial pressure) indices were measured before, during, and afte r bilateral infusion of NPY (1.0, 0.2, 0.04 mu g in 1 mu l synthetic C SF) into the PVN of conscious resting rats. Administration of the high est dose (1.0 mu g/mu l) caused bradycardia and reduced circulating no repinephrine levels without effecting circulating fuels, insulin or ep inephrine. In a second experiment, feeding-induced changes in hormonal and metabolic indices were assessed after NPY administration (1.0 mu g/mu l) into the PVN. During and after feeding, NPY enhanced the feedi ng-induced insulin response (P < 0.01) and attenuated the feeding-indu ced norepinephrine response (P < 0.05). The results of the present stu dy suggest that stimulation of NPY receptors in the PVN decreases symp athetic activity and increases parasympathetic activity in resting con ditions, and that these effects are potentiated during feeding.