Antagonism of the 5-HT-induced bronchoconstriction in the cat

In cats in which bronchoconstriction was induced and maintained by infusion of 5-HT, the bronchodilator effects of ketanserin, a related compound, cyproheptadine, clenbuterol and aminophylline were compared. The novel 5-HT2 antagonists ketanserin and R50970 were active in doses of about 10 nmol/kg, cyproheptadine was about 5 times less potent, but had a longer duration of action. Clenbuterol and aminophylline were only partially effective against 5-HT-induced bronchoconstriction. There was no reliable effect of the 5-HT antagonists against carbachol-induced bronchoconstriction.