Effect of beta adrenoreceptor blocking drugs on the responses of isolated rat mesenteric arteries.

The effect of several beta-blockers on the vasoactive effect of several substances was studied on the perfused isolated rat mesenteric vessels. The agonists were tested while the beta-blocker was infused; the effects were compared in the same experiment with those observed in a control period in which the agonists were injected without simultaneous infusion of beta-blocker. l-propranolol, infused at three different doses, did not modify the vascular effect of either angiotensin II (AII) or vasopressin (VP). On the other hand, the constrictor effect of epinephrine (E) and norepinephrine (NE) was significantly reduced. Timolol, but not sotalol, showed the same results. d-propranolol produced the same effect as l-propranolol. A high dose of l-propranolol did not protect alpha adrenoceptors of blockade induced by phentolamine.