An α-Adrenoceptor-Blocking Action of SGB-483, a New Piperazine Antihypertensive Agent in Isolated Vascular Smooth Muscles

摘要

SGB (10-7–10–5M), a new piperazinyl antihypertensive agent, like prazosin (10–8_10–6M), a potent preferential α1-adrenoceptor antagonist, inhibited the contractile response of rabbit aorta to norepinephrine and methoxamine in a competitive manner whereas in the cat coronary and rabbit basilar artery, the inhibition by SGB was not a competitive one. The potency of the inhibitory action of SGB was less than that of prazosin in all preparations used. Neither SGB nor prazosin had any inhibitory effect on the response to potassium, 5-hydroxytryptamine, prostaglandin F2α, and excess Ca2+ in all preparations. In the rabbit aortic membrane preparation, the specific binding of 3H-prazosin was inhibited, concentration-dependently, by SGB with IC50 value of 1.4 ± 0.09 µM. These studies indicated that SGB has an α1-adrenoceptor-blocking action though its potency is weaker t