Five inhibitory transmitters coexist in pelvic autonomic vasodilator neurons

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Abstract
HERE we describe the localization of a potent vasodilator, calcitonin gene-related peptide (CGRP), in pelvic autonomic neurons containing four other inhibitory transmitters: vasoactive intestinal peptide (VIP), neuropeptide Y, nitric oxide and acetylcholine. These neurons mediate endothelium-independent vasodilation by releasing nitric oxide and one or more neuropeptides. Sixty percent of nerve cell bodies in guinea-pig paracervical ganglia with immunoreactivity (IR) for VIP, choline acetyltransferase (ChAT) and nitric oxide synthase (NOS), also contained IR for CGRP. Furthermore, many VIP-IR varicose nerve terminals at the adventitia—medial junction of the guinea-pig uterine artery contained IR for CGRP, ChAT and NOS. Both α-hCGRP and β-hCGRP were potent dilators of the uterine artery (pD2 values 8.1, 8.3, respectively), but 1 μM hCGRP(8-37) did not antagonize dilations produced by either agonist. Dilations produced by α-hCGRP were unaffected by removal of the endothelium. Taken together with results of our previous studies, we propose that CGRP can contribute directly to autonomic vasodilation, possibly via CGRP2 receptors on smooth muscle cells, and that CGRP is the fifth inhibitory transmitter co-existing in pelvic vasodilator neurons.

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