Distribution of neuropeptide-like immunoreactive nerve fibers in the canine larynx.

The distribution of neuropeptide immunoreactive nerve fibers in the canine larynx was examined. In the epithelium of supra- and subglottic regions, a dense distribution of substance P (SP)- and calcitonin gene-related polypeptide (CGRP)-immunoreactive (IR) nerve fibers was observed. Some vasoactive intestinal polypeptide (VIP)-IR intraepithelial nerve fibers were also seen in the subglottic region. In the laryngeal glands, a dense distribution of VIP-IR nerve fibers with a few SP- and enkephalin (ENK)-IR nerve fibers were found around the acini. In the walls of arteries in the lamina propria, many VIP-, SP-, and CGRP-IR nerve fibers were seen, whereas neuropeptide Y-, ENK-, and VIP-IR nerve fibers were predominantly distributed around the arteries in the vocal muscle. In the free edge of the vocal cord, few immunoreactive nerve fibers were detected within the epithelium and around the arteries in the lamina propria. These results suggest that there are regional differences in the occurrence of peptides in nerve fibers innervating the epithelium and the blood vessels in the larynx and that the perception mechanism of the epithelium and the regulatory system of local blood flow are varied according to their location in the larynx.