The bronchoconstrictor action of the tetradecapeptide bombesin in the guinea-pig

The tetradecapeptide bombesin was found to exert a potent spasmogenic action on the bronchiolar muscle of the anaesthetized guinea-pig. The threshold bronchoconstrictor dose ranged between 50 and 200 ng kg−1. Other spasmogenic substances tested in the same experimental conditions, except physalaemin, were much less effective. Since antagonists of acetylcholine, histamine or 5-hydroxytryptamine did not inhibit the bronchoconstriction it is suggested that bombesin acts either by direct stimulation of the smooth muscle or by the prior release of other, as yet unidentified, spasmogenic substances.