CUTANEOUS VASOMOTOR EFFECTS OF NEUROPEPTIDE-Y

The effects of neuropeptide Y (NPY) were examined on the cutaneous mic rovascular blood flow (CMF) of the hindpaws in anesthetized rats. NPY (0.5-50 nmol/kg), infused intraarterially into the hindpaw circulation , produced sustained dose-dependent increases in CMF (29 +/- 7% to 210 +/- 52%) indicating cutaneous vasodilation. Denervation of a hindpaw, ganglionic or a-adrenergic blockade significantly elevated the restin g CMF indicating tonic vasoconstrictor sympathetic input to the cutane ous vasculature. In the denervated hindpaw or following ganglionic blo ckade, NPY produced sustained decreases in CMF (up to 51 +/- 8%) indic ating vasoconstriction. Effects of the Y-1 receptor agonist, (Leu(31), Pro(34)) Npy were identical to those of NPY. The Y-2 receptor agonist , NPY13-36 increased CMF of the intact hindpaw (24 +/- 10%-68 +/- 16% at 5-150 nmol/kg, i.a.) but did not affect CMF of the denervated hindp aw. NPY and (Leu(31), Pro(34)) NPY, but not NPY13-36, produced signifi cant presser effects. These data suggest that: 1) NPY produces neuroge nic cutaneous vasodilation via presynaptic Y-2 receptor-mediated inhib ition of sympathetic tone, 2) Y-1 receptors may also exist presynaptic ally, however, it is likely that (Leu(31), Pro(34)) NPY does not disti nguish between Y-1 and Y-2 receptors, and 3) activation of postsynapti c Y-1 receptors produces vasoconstriction which is unmasked only when the noradrenergic tone is eliminated.