Neuropeptide Y (NPY): enhancement of blood pressure increase upon alpha-adrenoceptor activation and direct pressor effects in pithed rats.

The effects of neuropeptide Y (NPY) on blood pressure and heart rate were studied in pithed rats. Systemic infusion of NPY in a dose (230 pmol X kg-1 X min-1) which per se did not affect blood pressure enhanced the pressor response to phenylephrine (50 nmol X kg-1 i.v.) and that to electrical stimulation of the sympathetic outflow. In higher doses, NPY caused a pressor effect per se, which was dose-dependently antagonized by nifedipine but not by adrenoceptor antagonists. In conclusion, NPY enhanced the alpha-adrenoceptor-mediated response and had Ca2+-dependent vasoconstrictor activity in vivo.