Tyrosine hydroxylase- and neuropeptides-immunoreactive nerves in canine trachea

Abstract

Objective: To determine distribution of catecholaminergic and peptidergic nerve fibers in canine tracheas by use of immunohistochemistry.

Sample population: 10 tracheas collected from healthy adult dogs after euthanasia.

Procedure: Structure of the nerve network and distribution of tyrosine hydroxylase (TH)- and 6 types of neuropeptide-containing nerves in canine tracheas were immunohistochemically studied, using neurochemical markers.

Results: Intraepithelial free nerve endings with immunoreactivity for calcitonin gene-related peptide (CGRP) and substance P (SP) were observed. Tyrosine hydroxylase-, SP-, vasoactive intestinal peptide (VIP)-, and galanin (GAL)-immunoreactive nerve fibers were observed within and around the submucosal seromucous gland. In the smooth muscle layer, numerous TH- and GAL-immunoreactive nerve fibers, a moderate number of VIP- and neuropeptide Y (NPY)-immunoreactive nerve fibers, and a few SP- and methionine enkephalin (ENK)-immunoreactive nerve fibers were observed. Numerous nerve cell bodies with VIP and GAL immunoreactivity and a few with SP ENK, and NPY immunoreactivity were observed. Many TH-immunoreactive fibers were arranged in a meshwork around blood vessels. Nerves with CGRP-, SP-, VIP-, GAL-, ENK-, and NPY-immunoreactivity were also observed around blood vessels.

Conclusions: Complex innervation, including catecholamine- and neuropeptide-containing nerves, which may be related to regulation of muscle contraction and glandular secretion, are found in canine tracheas.