α-Adrenoceptor blocking action of aaptamine, a novel marine natural product, in vascular smooth muscle

Abstract

Abstract In the rabbit isolated aorta and renal artery, aaptamine (3 times 10−5  m), a novel heteroaromatic substance isolated from a sea sponge Aaptos aaptos produced a parallel, rightward shift of the dose-response curve for noradrenaline, whereas that for histamine or KCl was not affected. But, the derivatives of aaptamine, demethylaaptamine, demethyloxyaaptamine, dihydroaaptamine and dihy-drodemethylaaptamine at concentrations of 10−5 to 10−4  m had no effect on the dose-response curve for noradrenaline. These results suggest that aaptamine is a competitive antagonist of α-adrenoceptors in vascular smooth muscles.