Abstract
Using a new preparation for perfusing the bronchial artery in the dog, the bronchomotor and vasomotor activities in the bronchial circulation system of several physiologically active amines were investigated. The right bronchial artery was cannulated and perfused with the dog's own blood delivered from the femoral artery in the anesthetized and immobilized dog. The bronchomotor and vasomotor tones were measured continuously. Drugs were injected into the perfused bronchial artery. Acetylcholine, pilocarpine, histamine, serotonin and nicotine caused bronchoconstriction, the duration being within one minute for ACh and nicotine, several minutes for histamine and serotonin, and 10 to 20 minutes for pilocarpine. The order of bronchoconstrictor activity was as follows: Serotonin>histamine>ACh>pilocarpine>nicotine. The amines produced a vasodilatation of the bronchial vascular bed, except that serotonin evoked either vasodilatation or vasoconstriction. Pretreatment with atropine (0.5mg/kg i.v.) completely abolished the bronchomotor and vasomotor responses to ACh, pilocarpine and nicotine, and inhibited the increase in overflow produced by histamine by 47%. The responses to serotonin were not altered by atropine pretreatment. In this study, the bronchomotor and vasomotor responses in the bronchial circulation system to the physiologically active amines were clarified, and were discussed on the basis of the physiological and pathological roles of the amines and, also in terms of differences between the in vivo and in vitro responses to the amines.
