Studies on cardiac distribution and function of neuropeptide Y.

High concentrations of a novel peptide, neuropeptide Y, have been demonstrated in the guinea-pig and canine heart and in the latter, a particularly high concentration was found in the region of the coronary vasculature (126 +/- 31 pmol g-1). Intra-arterial infusion of neuropeptide Y for 30 s into the coronary artery of the intact, innervated dog heart resulted in a rapid and short-lasting reduction of blood flow from 38 +/- 4 to 31 +/- 3 ml min-1 (P less than 0.05) to resume control level, 39 +/- 5 ml min-1, within 5 min. These injections were unaccompanied by changes in heart rate and aortic pressure, while there was an associated small reduction in dP/dt, used as a measure for changes in contractility. In vitro studies using the isolated, paced papillary muscle from cat, guinea-pig and rat, and spontaneously beating right atria from the guinea-pig, demonstrated no effect of NPY on active tension or beating frequency. The results indicate that NPY has vasoconstrictor properties, but under the test circumstances to lack both positive and negative inotropic and chronotropic effects.