[Studies on the blood pressure of beta-adrenoceptor blocking drugs, particularly in relation to the mechanism of the pressor action induced by beta-adrenoceptor blocking drugs in rats (author's transl)].

Several investigators have confirmed that beta-adrenoceptor blocking drugs produced a sustained pressor action in anesthetized rats. However, the mechanism of the pressor action has not been sufficiently explored. The following studies were done to further investigate the mechanism. (a) effects of pindolol, carteolol, propranolol, alprenolol, practolol and acebutolol (0.015-0.3 mumole/kg i.v.) on blood pressure of anesthetised rats, b) effects of these drugs on the positive chronotropic action and vasodilation induced by isoprenaline (0.1 microgram/kg i.v.) in anesthetized rats, c) effects of these drugs on the increase in heart rate and contractile force of isolated rat and guinea pig atria induced by isoprenaline, d) effects of these drugs on the relaxation of isolated guinea pig trachea induced by isoprenaline. From these experiments, the magnitude of the pressor action of beta-adrenoceptor blocking drugs in anesthetized rats was found to be more closely related to the magnitudes of inhibition produced by beta-adrenoceptor blocking drugs on isoprenaline-induced relaxation of isolated guinea pig trachea and on isoprenaline-induced vasodilation in anesthetized rats than to those on isoprenaline-induced positive chronotropic and inotropic actions of isolated atria.