Alpha-adrenoceptor blocking action of aaptamine, a novel marine natural product, in vascular smooth muscle

In the rabbit isolated aorta and renal artery, aaptamine (3 X 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 dihydrodemethylaaptamine 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 alpha-adrenoceptors in vascular smooth muscles.