Vagal afferents contribute to exacerbated airway responses following ozone and allergen challenge

Brown-Norway rats (n = 113) sensitized and challenged with nDer f 1 allergen were used to examine the contribution of lung sensory nerves to ozone (O-3) exacerbation of asthma. Prior to their third challenge rats inhaled 1.0 ppm O-3 for 8h. There were three groups: (1) control; (2) vagus perineural capsaicin treatment (PCT) with or without hexamethonium; and (3) vagotomy. O-3 inhalation resulted in a significant increase in lung resistance (R-L) and an exaggerated response to subsequent allergen challenge. PCT abolished the O-3-induced increase in R-L and significantly reduced the increase in R-L induced by a subsequent allergen challenge, while hexamethonium treatment reestablished bronchoconstriction induced by allergen challenge. Vagotomy resulted in a significant increase in the bronchoconstriction induced by O-3 inhalation and subsequent challenge with allergen. In this model of O-3 exacerbation of asthma, vagal C-fibers initiate reflex bronchoconstriction, vagal myelinated fibers initiate reflex bronchodilation, and mediators released within the airway initiate bronchoconstriction. (C) 2012 Elsevier B.V. All rights reserved.