CONTRACTILE RESPONSE TO NEUROPEPTIDE-Y OF RAT ISOLATED DUODENUM

The response of isolated duodenum to neuropeptide Y (NPY) was studied isotonically in neonatal and adult rats. Neuropeptide Y (10(-8) to 10( -6) M) elicited a biphasic contraction of isolated duodenum from neona tal rats, but monophasic and weak contraction of adult duodenum. The f irst phase of NPY-induced contraction of neonatal duodenum was concent ration dependent and partially inhibited by preincubation with tetrodo toxin, a Na+ channel blocker, hyoscine, a muscarinic antagonist, suram in, a P2 purinoceptor antagonist, and indomethacin, an inhibitor for p rostaglandin biosynthesis. Neuropeptide Y(13-36), a Specific Y2 NPY re ceptor agonist, elicited a concentration-dependent contraction of neon atal rat duodenum. The duodenal response to NPY thus changes during de velopment in rats. Both cholinergic and purinergic transmission and pr ostaglandin biosynthesis may be involved in the NPY-induced contractio n of neonatal duodenum. Neuropeptide Y-induced contraction may be medi ated through presynaptic Y2 receptors.