CGRP and substance P in intraepithelial neuronal structures of the human upper respiratory system

The distribution of intraepithelial nerve fibres and neuroendocrine cells within the surface and glandular epithelium of human nasal mucosa and larynx was examined using immunohistochemical techniques. Neuronal structures were immunostained for the general neuroendocrine marker protein gene-product (PGP) 9.5, and the two neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) using immunofluorescence and streptavidin-biotin-peroxidase complex (S-ABC) methods. Intraepithelial nerve fibres with free nerve endings contained PGP 9.5 and were found within the respiratory surface epithelium of the nasal mucosa and the squamous epithelium of the larynx. A subpopulation of these nerve fibres showed positive immunoreactivties with antibodies against SP and CGRP. Nerve fibres within the ductal epithelium of subepithelial excretory ducts passing the basal membrane and reaching the luminal part were detected. These nerve fibres showed CGRP-like immunoreactivity but not for SP. A dense network of nerve fibres within the squamous surface epithelium was detected in the subglottic and epiglottic region containing CGRP and SP in a small subpopulation of nerve fibres. Single intraepithelial taste buds in the epiglottic region and neuroendocrine cells within the subglottic epithelium expressed PGP 9.5.