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

The study focuses on examining the distribution of specific nerve fibers in the nasal mucosa of horses. Researchers analyzed nasal tissue samples to determine the presence and distribution of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and intermediate neurofilaments. Interestingly, the density of nerve fibers containing CGRP or SP in horse nasal mucosa was found to be similar to other species, while the expression of VIP was low.

Objective and Methodology

• The primary objective of the research was to investigate the distribution of nerve fibers containing CGRP, SP, VIP, and intermediate neurofilaments in the nasal mucosa of healthy horses.
• The researchers gathered full-thickness nasal tissue specimens from the rostral section of the nasal septum of six horses that showed no evidence of nasal disease.
• These specimens were analyzed using fluorescence immunohistochemistry, which is a technique that uses antibodies to detect specific proteins in tissues.

Key Findings

• Immunohistochemistry revealed that nerve fibers with CGRP-like and SP-like immunoreactivity formed a dense subepithelial network, with many fibers found in between epithelial cells. These fibers were also associated with blood vessels and mucous glands.
• In contrast, there were fewer fibers with VIP-like immunoreactivity, implying a lower expression of VIP.
• Intermediate neurofilaments were found primarily in large nerve fiber bundles present near elements like the nasal septum and mucous glands, suggesting a considerably high expression. However, their density did not align with the density of fibers expressing SP or CGRP.

Conclusion and Implications

• The researchers concluded that in the nasal mucosa of horses, the density and distribution of nerve fibers expressing SP or CGRP resemble those found in other species, supporting their potential ubiquitous nature in nasal nerve fiber distribution.
• Conversely, the low expression of VIP indicates a possible difference in the role or mechanism of VIP nerves in the horse nasal mucosa compared to other species.
• While intermediate neurofilaments were found across many nerve fibers, their distribution did not seem to correspond with small diameter fibers expressing either SP or VIP.