Effects of tryptamine antagonists on the anaphylactic contractions of the bovine pulmonary smooth muscles

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Abstract
Calves were sensitized with horse plasma (H.P.), 0.2 ml/kg, i.v., and H.P. (0.2 ml/kg) in Freund''s complete adjuvant, s.c. The latter injection was repeated 1 wk later and the animals were killed 10 days after the second injection. Spirally cut strips of pulmonary artery and vein and the trachealis muscle from the sensitized calves contracted to 5-hydroxytryptamine (5-HT) and specific antigen (horse plasma). Antigen-induced contractions of the pulmonary smooth muscles were significantly blocked (P < 0.05) by the 5-HT antagonists, methysergide and ketanserin. The trachea appeared less sensitive to the antagonists than the pulmonary vessels. 5-HT apparently participates in the pulmonary anaphylactic reactions of cattle and ketanserin may be useful in suppressing bovine pulmonary hypersensitivities.