Pharmacology of BMY 20064, a potent Ca super(2+) entry blocker and selective alpha sub(1)-adrenoceptor antagonist

BMY 20064 is a dihydropyridine Ca super(2+) entry blocker with potent and selective alpha - sub(1)-adrenoceptor antagonist properties. The drug was equal in potency to nifedipine as a Ca super(2+) entry blocker in depolarized smooth muscle preparations. It was less active than nifedipine in antagonizing Ca super(2+)-induced contractions of isolated guinea pig papillary muscles paced at 0.2, 1.0, or 2 Hz. BMY 20064 was a potent (0.1-0.2 x prazosin) and selective alpha sub(1)-adrenoceptor antagonist in radioligand binding assays and in ganglion-blocked anesthetized rats challenged with phenylephrine. BMY 20064 blocked both the K super(+) and alpha sub(1)-adrenergic agonist-induced increases in super(45)Ca uptake into rabbit aortic rings.