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Tyrosine hydroxylase- and neuropeptides-immunoreactive nerves in canine trachea.

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.