Expression of vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, and intermediate neurofilaments in nasal mucosal nerve fibers of horses without nasal disease

Objective-To determine the distribution of nerve fibers containing calciton in gene-related peptide (CGRP), substance P (SP), vasoactive intestinal pep tide (VIP), and intermediate neurofilaments in nasal mucosa of horses. Animals-6 horses without evidence of nasal disease. Procedure-Full-thickness nasal tissue specimens were obtained from the rost ral portion of the nasal septum at necropsy, and fluorescence immunohistoch emistry was performed to assess mucosal distribution of nerve fibers. Results-Nerve fibers with CGRP-like immunoreactivity (CGRP-Li) formed a den se subepithelial network, and a large number of fibers were found coursing between epithelial cells. Fibers with CGRP-Li were also associated with blo od vessels and mucous glands. Fibers with SP-like immunoreactivity (SP-Li) had a similar distribution and density. In contrast, there were few fibers with VIP-like immunoreactivity. Fibers containing intermediate neurofilamen ts were prominent and appeared as large nerve fiber bundles mainly adjacent to the nasal septum but also close to mucous glands and within the lamina propria. Intermediate neurofilaments were also identified in single nerve f ibers at all sites, but the density of fibers with intermediate neurofilame nts did not match that of fibers with CGRP- or SP-Li. Conclusions-The density and distribution of nerve fibers containing SP- or CGRP-Li in nasal mucosa of horses was similar to that reported for other sp ecies. However, expression of VIP in nerve fibers was low. Antibodies again st intermediate neurofilaments identified many nerve fibers in nasal mucosa of horses but did not appear to identify small diameter fibers expressing SP or VIP. (Am J Vet Res 2000;61:1619-1624).