Functional Antagonism between Endogenous Neuropeptide Y and Calcitonin Gene-Related Peptide in Mesenteric

To test the hypothesis that endogenous neuropeptide Y (NPY) counteracts the vasodilator effects of calcitonin gene-related peptide (CGRP), we used isolated mesenteric resistance arter-ies of rats and mice. With immunohistochemistry, we observed CGRP-containing fibers along and in the vicinity of a subset of NPY- or tyrosine hydroxylase-immunoreactive fibers. The CGRP1 receptor component calcitonin-related-like receptor was expressed by periarterial nerves and smooth muscle cells, whereas receptor activity-modifying protein 1 was ob-served primarily on the smooth muscle. In organ chambers, exogenous CGRP caused relaxations that were reversed by exogenous NPY. The effects were inhibited by 1-piperidin-ecarboxamide, N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]-carbonyl]pentyl]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)