A NEW BETA-ADRENOCEPTOR BLOCKING-AGENT DERIVED FROM DEHYDROZINGERONE

1. Dehydrozingeronolol (DZPN; 0.1, 0.5, 1.0 mg/kg, i.v.) produced a do se-dependent bradycardia response and a sustained presser action in ur ethane-anesthetized normotensive rats. DZPN inhibited the tachycardia effects by (-)isoproterenol, but had no blocking effect on the arteria l presser responses induced by phenylephrine. 2. In in vitro study, DZ PN antagonized (-)isoproterenol-induced positive chronotropic effects in guinea-pig isolated right atria and relaxation responses in rat iso lated uterus horns. 3. DZPN causes mild direct cardiac depression at h igh concentrations without intrinsic sympathomimetic activity (ISA). 4 . The order of potency of beta-adrenoceptor antagonists in competing f or the [3H]dihydroalprenolol binding sites was (-)propranolol>> DZPN g reater than or equal to atenolol.