Vasodilative effects of indole alkaloids obtained from domestic plants, Uncaria rhynchophylla Miq. and Amsonia elliptica Roem. et Schult.

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Abstract
Vasodilative effects of hirsutine (HS) and hirsuteine (HST) which were isolated from the domestic plant Uncaria rhynchophylla MIQ. and .beta.-yohimbine (.beta.-Y) which was isolated from the domestic plant Amsonia elliptica ROEM. et SCHULT. were carried out. In the hind-limb artery of anesthetized dogs, intra-arterial administration of HS, HST and .beta.-Y caused a vasodilatation. The vasodilative potency of HS was somewhat stronger than that of HST, and the potency of both alkaloids was approximately equal to that of papaverine. The vasodilative effect of .beta.-Y was similar to that of yohimbine, which is considered to be derived from its .alpha.-adrenoceptor blocking effect, and the potency of both alkaloids was approximately the same, while the effect of .beta.-Y was stronger than that of papaverine. In the coronary artery, HS showed a vasodilation and its potency was weaker than that of papaverine. Also, HS showed the same effect in the cerebral artery, and the potency of HS was approximately the same as that of papaverine. These results suggest that the mode of the vasodilative effect induced by HS may partly differ from that of papaverine.