Regional differences in the responsiveness of isolated arteries from cattle, dog and man.

Changes in tension of spiral strips from basilar, external carotid, temporal and muscle arteries from cattle, dog and man were monitored isometrically. Dose-response curves for 5-HT, noradrenaline and ergotamine indicated a variation in responsiveness between different arteries of the same species as well as between the same arteries of different species. When tested against 5-HT ergotamine consistently acted as non-competitive dualist but it antagonized responses to to noradrenaline only in peripheral arteries from dog and man. In all arteries from the carotid vasculature and in bovine muscle arteries the vasoconstrictor effects of ergotamine and noradrenaline were independent additive. It is suggested that the therapeutic value of ergotamine in the treatment of migraine headache is due to its selective vasoconstrictor activity in the external carotid vasculature mediated through independent additive vasoconstrictor effects of ergotamine and noradrenaline.