Newly synthesized alpha 1-adrenoceptor blockers (SM911 and SM2470) and characterization of alpha-adrenoceptors in rat aortic strips, rat vas deferens preparations and rabbit aortic strips.

Alpha 1-adrenergic potencies of SM911 and SM2470, whose chemical structures are similar to that of prazosin, a selective alpha 1-adrenoceptor blocker, were tested in rabbit aortic strips, rat aortic strips and rat vas deferens preparations. SM2470 was as potent as prazosin in alpha 1-adrenoceptor blocking effects, though SM911 was 0.5-0.1 as potent as prazosin. The pA2-values for prazosin, SM911 and SM2470 were approximately one order of magnitude lower in rabbit aortic strips and rat vas deferens preparations than in rat aortic strips, suggesting that alpha 1-adrenoceptors in these tissues may not be identical. SM911 and SM2470 as well as prazosin did not interact with alpha 2- and beta-adrenoceptors, muscarinic and nicotinic cholinoceptors, and histamine and serotonin receptors in doses up to 10(-5) M.