Neuropeptide Y and control of vascular resistance in skeletal muscle.

The effect of neuropeptide Y (NPY) on the increase in skeletal muscle vascular resistance caused by exogenous noradrenaline and by sympathetic stimulation was examined in gracilis muscles of anaesthetised dogs. NPY potentiated the increases in resistance caused by both of these to similar degrees. Although NPY itself often caused an elevation in the basal resistance, correlation coefficients for the percentage increase in basal resistance due to NPY and the percentage increase in the evoked sympathetic and noradrenergic responses in the presence of NPY indicated that it was the NPY itself (rather than the increase in basal resistance per se) which was responsible for the potentiation. The potentiation was apparently biphasic, with an initial peak in response during the first 20 min following administration of NPY followed by a secondary peak between 30 and 60 min. Radioimmunoassay for plasma levels of NPY indicated that the secondary increase of vascular resistance was not associated with a secondary peak in the plasma level of NPY.