Response of rat lung to humoral mediators of anaphylaxis and its modification by drugs and sensitization.

1 The effects of humoral mediators of anaphylaxis on the bronchial function of the pithed rat have been assessed and compared with their effects in the guinea-pig and man. 2 5-Hydroxtryptamine, acetylcholine and bradykinin were bronchoconstrictor. Slow reacting substance in anaphylaxis and prostaglandin F2a caused only slight constriction at high doses and histamine was not active. 3 Bradykinin was less active in the rat than in the guinea-pig and its effects were not antagonized by anti-inflammatory analgesic drugs. 4 beta-Adrenoceptor blockade potentiated the activity of bradykinin but not that of 5-hydroxytryptamine or acetylcholine. 5 Dexamethasone reduced the activity of bradykinin but not that of 5-hydroxytryptamine or acetylcholine. 6 Sensitization with Nippostrogylus brasiliensis did not increase the sensitivity of the rat lung to the effects of mediators.