Morphology of the nerve endings in laryngeal mucosa of the horse

To discuss the significance of laryngeal sensation on various disorders of the horse, we studied the morphological and topographical characteristics o f sensory structures in the laryngeal mucosa using immunohistochemistry and immunoelectron microscopy, Various sensory structures, i.e. glomerular end ings, taste buds and intraepithelial free nerve endings, were found in the laryngeal mucosa by immunohistochemistry for protein gene product 9.5 (PGP 9.5) and neurofilament 200kD (NF200), Glomerular nerve endings were distrib uted mainly in the epiglottic mucosa; some endings were also found in the a rytenoid region arising from thick nerve fibres running through the subepit helial connective tissue. Some terminals directly contacted the epithelial cells. Taste buds were distributed in the epithelium of the epiglottis and aryepiglottic fold, In the whole mount preparation, the taste buds were sup plied by the terminal branching of the thick nerve fibres, In same cases, t he taste buds were arranged around the opening of the duct of the epiglotti c glands, The intraepithelial free nerve endings were found to he immunorea ctive for substance P (SP) and calcitonin gene-related peptide (CGRP). Thes e nerve endings were surrounded by the polygonal stratified epithelial cell s in the supraglottic region, and hy the ciliated cells in the subglottic r egion. The density of the intraepithelial free nerve endings was highest in the corniculate process of the arytenoid region and lowest in the vocal co rd mucose. The densities of CGRP- and SP-immunoreactive nerve endings in th e arytenoid region were (mean +/- s.d.) 30.6 +/- 12.0 and 10.0 +/- 4.9 per unit epithelial length (I mm), respectively and in the vocal fold mucosa, 1 .1 +/- 0.9 and 0.8 +/- 0.7, respectively. Approximately one half of the CGR P immunoreactive nerve endings were immunoreactive for SP and most SP-immun oreactive nerve endings were also immunoreactive for CGRP. Well-developed s ubepithelial plexus with numerous intraepithelial fibres were observed in f iat or round mucosal projections that existed on the corniculate process of the arytenoid region. In conclusion, the laryngeal mucosa of the horse see ms to have morphology- and/or location-dependent sensory mechanisms against various endo-and exogenious stimuli.