Methods:12 male mangles were included in this study.The bronchoconstriction was induced by intratracheal infusion of methacholine.

• 方法：选取12只雄性杂种犬采用交叉设计、自身对照的方法进行实验，采用向气管内注入乙酰甲胆碱的方法使气道平滑肌痉挛。