EFFECTS OF CYPROHEPTADINE, RITANSERIN AND Ca2+ ON RAT AORTIC REACTIVITY TO 5-HYDROXYTRYPTAMINE

Abstract

A study was undertaken to determine whether the similarity in the profile of action of Ketanserin (a 5HT2 receptor antagonist and a series of L-type Ca2+ channel antagonists previously reported (1,2) is shared by other chemically unrelated 5HT2 receptor antagonists.  Cyproheptadine and ritanserin in nanomolar concentrations potently suppressed 5HT-induced contractions of rat aortic strip non-surmountably.  Increasing buffer Ca2+ concentrations from 2.0 mM to 5.0 mM in the continued presence of the same concentrations of each drug attenuated the expected rise in the inhibitory activity of these compounds over time.  These findings are strikingly similar to those previously noted with ketanserin.  Together with previous data (1-4), the present observations suggest overlap in the pharmacology of 5HT2 receptor antagonists and L-type Ca2+ channel antagonists.