Vascular beta-adrenoceptor stimulating properties of phenylephrine.

In pithed rats pretreated with propranolol changes occurred in the slopes of dose--pressor response curves to i.v. phenylephrine and noradrenaline but not to LD 3098, a pure alpha-adrenoceptor stimulant. In dogs, cats, and spontaneously hypertensive rats pretreated with an alpha-adrenoceptor blocker, i.v. phenylephrine induced vasodilatory responses which were antagonised by propranolol. These results indicate that phenylephrine, in addition to its known beta1-agonistic properties, stimulates the vascular beta2-adrenoceptors.