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

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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.