ROLE OF CAPSAICIN-SENSITIVE TRIGEMINAL NERVES IN DEVELOPMENT OF HYPERREACTIVE NASAL SYMPTOMS IN GUINEA-PIG MODEL OF NASAL ALLERGY

The effect of capsaicin pretreatment on frequency of sneezing, decreas e of nasal patency, and increase of vascular dye leakage induced by an tigen or histamine challenge on the guinea pig nasal mucosa was invest igated. The animals were sensitized intraperitoneally with ovalbumin. Capsaicin pretreatment significantly inhibited sneezing induced by nas al challenge with histamine and antigen, indicating that capsaicin-sen sitive sensory nerves constitute an afferent pathway of the sneezing r eflex in nasal allergy. Although capsaicin pretreatment tended to inhi bit the decrease of nasal patency and the increase of vascular dye lea kage of the nasal mucosa induced by antigen challenge, this tendency w as not statistically significant. The present study indicated that the participation of a local reflex via capsaicin-sensitive trigeminal ne rves in nasal vascular responses observed after antigen challenge in t he guinea pig model of nasal allergy is rather small compared to the l arge direct vascular effects of chemical mediators released from basop hilic cells in the nasal mucosa.