Basenji-Greyhound dog model of asthma: influence of atropine on antigen-induced bronchoconstriction.

To test the relative importance of cholinergic effects on the Basenji-Greyhound (BG) model of asthma, we administered Ascaris antigen to Ascaris-sensitive BG dogs without other treatment, and following intravenous atropine. Pulmonary resistance (RL) increased from 1.4 +/- 0.43 cmH2O . l-1 . s (mean + SE) to 26.0 +/- 5.21 after Ascaris antigen exposure in seven untreated dogs. In the same dogs pretreated with 0.2 mg/kg atropine, RL increased from 1.5 +/- 0.31 to 18 +/- 5.00. Atropine 0.4 and 1.0 mg/kg did not result in increased protection. Although 0.2 mg/kg atropine markedly inhibited the airway responses to both inhaled citric acid and methacholine, it only slightly prevented antigen-induced airway constriction. We conclude that in BG dogs, cholinergic pathways elicit bronchomotor responses to irritants but that the major component of antigen-induced bronchoconstriction is not cholinergically mediated.