YM-430 is a β1 adrenergic receptor antagonist and a calcium channel antagonist. YM430 could be both an antianginal and antihypertensive agent. YM430 (10(-8)-10(-6) M) inhibited 3,4-diaminopyridine-induced rhythmic contractions with an IC50 value of 59.2 nM. In anesthetized rats, YM430 (10-100 mg/kg PO) inhibited arginine vasopressin-induced ST-segment depression with an IC50 value of 36.6 mg/kg PO.