Tyrosine hydroxylase- and neuropeptides-immunoreactive nerves in canine trachea

Immunohistochemical demonstration of lumbar intervertebral disc innervation in the dog

Low back pain is a common ailment in dogs, particularly in specific breeds such as the German shepherd dog. A number of structures such as facet joint capsules, ligaments, dorsal root ganglia, periosteum, vertebral endplates and meninges have been associated with this condition. Yet, in spite of all diagnostic efforts, the origin of pain remains obscure in a substantial proportion of all cases. A further structure often being involved in vertebral column disorders is the intervertebral disc. The presence of nerves, however, is a precondition for pain sensation and, consequently, structures lacking innervation can be left out of consideration as a cause for low back pain. Nerve fibres have been demonstrated at the periphery of the intervertebral disc in man, rabbit and rat. With regard to the dog, however, the extent of intervertebral disc innervation is still being disputed. The goal of the present study, therefore, was to substantiate and expand current knowledge of intervertebral disc innervation. Protein gene product (PGP) 9.5 was used for immunohistochemical examination of serial transversal and sagittal paraffin sections of lumbar discs from adult dogs. This general marker revealed nerve fibres to be confined to the periphery of the intervertebral discs. These results indicate that even limited pathological processes affecting the outer layers of the intervertebral disc are prone to cause low back pain.

Nerve plexuses in the trachea and extrapulmonary bronchi of the rat

Intrinsic nerve plexuses of the rat trachea and extrapulmonary bronchi were examined by immunohistochemistry. Three nerve plexuses--peritracheal and peribronchial, intramuscular, and submucosal--were found in the wall of the trachea and bronchi. Nerve cell bodies were located in the peritracheal and peribronchial nerve plexuses. They occurred singly or formed ganglia in the plexus, and regional differences in cell numbers were found in the cervical and thoracic portions of the trachea and in the extrapulmonary bronchia. In total, 83.5 +/- 28.3 ganglia (mean +/- SD, 57-131, n=5) and 749.8 +/- 221.1 nerve cell bodies (540-1,080, n=5) were found in the nerve plexus. The mean densities of ganglia were 0.31, 0.97 and 1.15/mm2, and the mean densities of the nerve cell bodies were 1.82, 9.26 and 11.54/mm2 in the cervical region, thoracic region of trachea, and extrapulmonary bronchi, respectively. Almost all nerve cell bodies in ganglia were positive for choline acetyltransferase and neuropeptide Y (NPY), and a few cells were positive for vasoactive intestinal peptide (VIP). In addition, in cholinergic nerves, a few nerve fibers in the smooth muscles were positive for substance P (SP), calcitonin gene-related peptide (CGRP), and VIP, and a moderate number of fibers were positive for NPY. Tyrosine hydroxylase-immunoreactive nerve fibers were observed around blood vessels and within nerve bundles in the tunica adventitia. In the epithelium, nerve fibers were positive for SP and CGRP. Our results indicate that postganglionic neurons form three layers of cholinergic plexuses in the rat trachea and extrapulmonary bronchi, and that all of these possess intrinsic and extrinsic peptidergic innervation.