The possible role of substance P in the allergic reaction, based on two different provocation models.

It was shown in two different provocation models (nasal and bronchial provocation) that substance P (SP) may play an important role in the neurogenic inflammatory response in upper and lower airway disease. (1) Pretreatment with SP augments the antigen challenge response of the nasal mucosa. (2) The baseline bronchoalveolar lavage (BAL) concentrations of SP are elevated 8-fold in allergies (pollen asthma) as compared with normals, even outside of season. (3) The SP concentration in BAL increases significantly (p less than 0.05) after bronchial allergen provocation. These findings support a previous hypothesis of an abnormally elevated activity of nonadrenergic-noncholinergic excitatory nerves and are in accordance with the results of a decreased activity of neutral endopeptidase exaggerating neurogenic inflammatory responses in the airways, including bronchomotor tone hyperresponsiveness.