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Schematic illustration showing how ozone stimulation of bronchial nerve fibers induces respiratory responses.
Figure 4: Ozone induces neurally mediated responses in the bronchial airways.Stimulation of nociceptive interepithelial nerve fibers by ozone leads to reflex cough and a decrease in maximal inspiration that is relieved by opioid agonists, which block sensory pathways. Two possible mechanisms are involved: (1) stimulation of irritant receptors contributes to cough and induces a vagally mediated reflex that increases airway resistance, probably via airway smooth muscle contraction that is blocked by atropine; (2) C fiber stimulation releases neurokinins such as substance P that dilate nearby capillaries, activate mucous glands, and contract airway smooth muscle via neurokinin receptors. Prostaglandin E2 released by epithelial cells exposed to ozone or to ozone reaction products also sensitizes C fibers.Source: Devlin et al. (1997)