A 80b

A-80b is a synthesized pyridazino[4,5-b]indole derivate with potent and long-lasting antihypertensive activity. The decrease in diastolic pressure was greater than the decrease in systolic pressure and cardiac frequency was not modified significantly. A-80b shows dose-dependent inhibition of the Ca (2+) -induced contraction. Hypotensive and antihypertensive effect of A-80b possibly attributable to vasodilator activity via interference with Ca2+ influx and probably Ca2+ mobilization from intracellular stores.