Local vagal responses in the lung periphery.

In previous work we studied responses to ozone (O3) in the lung periphery of anesthetized male mongrel dogs. O3 (0.1 ppm) delivered locally to the lung periphery through a bronchoscope wedged in a segmental airway increased collateral resistance (Rcs) 31.5 +/- 5%. Bilateral cervical vagotomy or pretreatment with atropine aerosol prevented these responses to O3. In the present study we asked two questions. First, is the vagus necessary for responses to 0.1 ppm O3 because it maintains base-line tone? Second, are physiological responses to O3 administered through a bronchoscope localized to the challenged region? To answer the first question, we increased base-line Rcs (38.4 +/- 11.8%) by administering an acetylcholinesterase inhibitor, neostigmine (aerosol), through the bronchoscope. Following neostigmine, O3 exposure increased Rcs (55.8 +/- 18.4%) only if the vagi were intact. To answer the second question, we introduced two bronchoscopes simultaneously into different regions of the lung. When O3 was delivered through one bronchoscope, responses were detected only in the exposed region. However, when the whole left lung was exposed to O3, the responses were also detected in the right lung, but only when the vagi were intact. We conclude that the lung has the capacity to respond to localized oxidant insult with vagally mediated responses limited to the region that is challenged. However, when a larger area is exposed, vagally mediated responses become generalized and affect both lungs.