Effects of neuropeptide Y on mean circulatory filling pressure in intact and ganglionic-blocked conscious rats

The dose-response effects of neuropeptide Y (NPY) and the vehicle, 0.9% NaCl, on mean arterial pressure (MAP), heart rate (HR) and mean circulatory filling pressure (MCFP), an index of body venous tone, were examined in conscious, intact and hexamethonium-treated rats. Saline infusions in intact and hexamethonium-treated rats did not significantly affect MAP, HR and MCFP. The i.v. infusion of NPY in intact rats dose dependently increased MAP, decreased HR, but did not alter MCFP. In the presence of hexamethonium, the pressor effect of NPY was enhanced, the lack of MCFP effect remained and the bradycardic effect was markedly attenuated. Our results suggest that NPY has moderate effects on MAP, but negligible effects on body venous tone.