[Pressor action of propranolol; with special reference to relationship between the pressor action and peripheral vascular tone].

We showed in previous studies that pro pranolol produced a pressor action in the rat, and that this action was also observed in the spinal rat infused with adrenaline, noradrenaline and a mixture of isoproterenol and vasopressin, but not with vasopression alone. The action was also observed in the guinea pig infused with adrenergic beta-stimulants. In the present work, conditions in the peripheral vessels in which propranolol observed in the spinal rat infused with a mixture of various doses of isoproterenol and vasopressin. The effect of propranolol on the blood pressure in guinea pigs and rabbits with a reduced vasoconstrictive tone in the peripheral vascular beds with alpha-blockade was studied. Propranolol produced a pressor action in the spinal rat infused with a mixture of isoproterenol and vasopressin, and the magnitude of the rise depended on the mixing rate of the doses of these two drugs. The drug also produced a sustained rise in blood pressure in guinea pigs and rabbits treated with alpha-blockers. Thus, it is concluded that propranolol produces a marked pressor action when peripheral vessels are maintained in conditions with an appropriate constrictive and beta-adrenoceptive vasodilator tone.