Origin and distribution of capsaicin-sensitive substance P-immunoreactive nerves in the nasal mucosa.

In immunohistochemical studies, substance P-immunoreactivity (SP-IR) was found in a population of trigeminal ganglion cells in guinea pig, rat and cat. SP-IR nerve endings were found in the spinal trigeminal nucleus, around sphenopalatine ganglion cells, around blood vessels, as well as under and within the epithelium of the nasal mucosa. Ligation and denervation experiments in the cat indicated that the SP-IR nerves in the sphenopalatine ganglion and the nasal mucosa are of trigeminal origin. Capsaicin pretreatment of guinea pigs and rats resulted in a selective loss of the SP-IR nerves in the nasal mucosa and sphenopalatine ganglion, while the parasympathetic and sympathetic nerves were still present.