Substance P (SP) is one of several
neuropeptides found in nasal mucosa. It exists primarily in sensory afferent neurons, which are best demonstrated by immunohistochemical staining. These
substance P-like immunoreactive (SPLI) nerve fibers are unmyelinated C fibers, which connect to the trigeminal ganglion and the spinal trigeminal nucleus. They are found around vessels and seromucinous glands in the submucosa. When the nasal mucosa receives a noxious stimulus, SP is released and acts orthodromically as a comediator of nasal
pain, while antidromically it induces vasodilatation, plasma extravasation, mucosal
edema, and
rhinorrhea. Its antidromic effects have been implicated in
vasomotor rhinitis and can be blocked by topical intranasal
capsaicin application. Wolf and others have demonstrated in human subjects that
vasomotor rhinitis can be blocked up to 1 year by a series of intranasal
capsaicin applications. It has not yet been demonstrated that nasal mucous SP levels following noxious nasal stimulus change after intranasal
capsaicin pretreatment. Consequently a project was designed to determine whether intranasal
capsaicin pretreatment would affect nasal
substance P release measured in nasal secretion. Nasal secretion SP levels were measured before and after noxious nasal stimulus in controls and in
capsaicin pretreated rats. The difference in measured nasal secretion SP levels were significant (p < 0.05).