Reactivity of the bronchial artery to 5-hydroxytryptamine

The activity of 5-hydroxytryptamine and its antagonism by the selective 5-HT2 serotonergic receptor antagonist, ketanserin, was tested on the bronchial arteries of three domestic species; bovine, equine and ovine. 5-hydroxytryptamine contracted the bronchial artery in the bovine (threshold: 1.0 X 10(-9) M), the equine (threshold: 1.0 X 10(-9) M) and ovine (threshold: 5.0 X 10(-9) M), dose-dependently. Ketanserin on the bronchial artery of the bovine (concentrations: 1.0 X 10(-9) M and 1.0 X 10(-8) M), equine (concentrations: 1.0 X 10(-10) M, 1.0 X 10(-9) M and 1.0 X 10(-8) M) and ovine (concentrations: 1.0 X 10(-10) M, 5.0 X 10(-10) M and 1.0 X 10(-9) M), significantly (p less than 0.05) shifted the concentration response curves to 5-hydroxytryptamine and caused a depression of the maximum at the higher concentrations. The data indicates the presence of 5-HT2 serotonergic receptors in the bronchial artery of these species. The depression may possibly be due to the antagonist's adrenolytic properties.