HEMODYNAMIC PROFILE OF NEUROPEPTIDE-Y IN DOGS - EFFECT OF GANGLIONIC BLOCKADE

The hemodynamic effects of neuropeptide Y (NPY) were examined over a d ose range of 0.03-30 nmol/kg, IV, in anesthetized, open-chest, ventila ted dogs with and without ganglionic blockade. In normal (non-ganglion -blocked) animals, NPY produced significant, dose-dependent, and susta ined (lasting 15-45 min) increases in mean arterial brood pressure and systemic vascular resistance (SVR) with a threshold dose of 0.3 nmol/ kg and a maximum effective dose of 10 nmol/kg. Cardiac index (CI) decr eased at doses > 1 nmol/kg, but stroke volume was not altered; heart r ate (HR) decreased significantly at and above the 3 nmol/kg dose. No s ignificant changes were observed in the left ventricular dP/dt (LVdP/d t) or the contractility index (LVdP/dt divided by systolic pressure). In ganglion-blocked animals, presser and SVR responses to NPY were sim ilar to those seen in normal animals but HR was not affected and a sma ll but significant decrease in CI was seen only at the 30 nmol/kg. Fur thermore, whereas LVdP/dt of ganglion-blocked dogs increased significa ntly at and above the 1 nmol/kg dose, the contractility index increase d slightly only with the 10 and 30 nmol/kg doses. These data indicate that NPY produces sustained hypertension in dogs secondary to peripher al vasoconstriction, has a weak, direct positive inotropic action on t he heart, and lacks chronotropic effects. (C) 1997 Elsevier Science In c.