MYOCARDIAL ELECTROPHYSIOLOGICAL EFFECTS OF NEUROPEPTIDE-Y IN DOGS

Neuropeptide Y (NPY) exerts coronary vasomotor and inotropic effects o n the canine heart. To test whether NPY also exerts regional myocardia l electrophysiological effects, dose-response and time course changes resulting from intravenous and regional intracoronary infusions of NPY were obtained in 14 alpha-chloralose-anesthetized dogs. Under constan t ventricular pacing, activation (A), recovery (R), and A-R interval ( ARI) maps were constructed from multiplexed unipolar surface electrogr ams recorded simultaneously from 64 sites within a 1.6 x 1.6-cm left v entricular region. Effects were compared with those of vasoactive inte stinal peptide (VIP) infusions and supramaximal left ansae subclaviae sympathetic nerve stimulation (SNS). The main finding was a uniform sh ortening of ARI, which reached a maximum of 8.7 +/- 1.2 ms, or 7% of c ontrol (P < 0.001), at about three times the baseline NPY plasma conce ntration (21.6 +/- 1.9 pg/ml). This effect decayed slowly (> 15 min) a long with NPY plasma levels. The effect of similar VIP infusions and o f SNS was 11%. Thus, compared with the previously identified maximal e ffect of adenylate cyclase activation (20%), exogenous NPY exerts a mo derate but markedly sustained ventricular myocardial electrophysiologi cal effect, which reaches maximum in relatively low plasma concentrati ons.