NPY (lng-10/ug) had no effect on mean arterial pressure (MAP) or heart rate (HR) when administered into the lateral brain ventricle or cisterna magna of conscious, chronically instrumented normotensive, male Wistar rats. However upon intravenous injection (0.1- 5/ug) it produced a dose related pressor response accompanied by bradycardia. This pressor effect was not influenced by prazosin infusion (100/ug/kg/min). These results suggest that NPY has no direct role in central cardiovascular regulation, but peripherally is a very potent vasoconstrictor peptide.