NEUROPEPTIDE Y-MEDIATED PRESSOR-RESPONSES FOLLOWING HIGH-FREQUENCY STIMULATION OF THE RAT SYMPATHETIC NERVOUS-SYSTEM

Neuropeptide Y (NPY) is a potent pressor agent that is stored in the s ympathetic nerves. In several species, NPY release is augmented when s ympathetic impulse frequencies increase. We investigated the extent to which NPY contributes to the pressor response to high- and low-freque ncy electrical stimulation. Rats were pithed, and the sympathetic trun k was stimulated at either 20 or 3 Hz in the presence or absence of an tagonists of NPY and alpha and beta adrenergic receptors. The 20-Hz st imulation raised plasma NPY levels, but the 3-Hz stimulation did not. The 20-Hz stimulation caused marked pressor responses that were mainta ined for several minutes after the end of stimulation regardless of wh ether rats were pretreated with adrenergic blockers. The NPY antagonis ts BIBP 3226 and 1229U91 reduced the size of the pressor response that followed 20 Hz stimulation by >50%. The rapid blood pressure spikes t hat occur during electrical stimulation are attenuated by alpha adrene rgic but not by NPY antagonists. There is a prolonged pressor response after high-frequency stimulation of the sympathetic trunk in pithed r ats that begins after 1 to 2 min of stimulation and lasts similar to 1 0 min after the end of stimulation. At least half of this pressor resp onse is mediated by NPY.