Cerebral microvessels contain A β2-adrenergic receptor

Abstract

Cerebral microvessels isolated from cat forebrain contain a specific β-adrenergic-sensitive adenylate cyclase. Among various compounds tested, the most potent activator of enzyme activity is isoproterenol (k a = 1.4 × 10 −7M), followed in order by epinephrine (k a= 1.5 × 10 −6M), norepinephrine (k a= 1.4 × 10 −5M) and phenylephrine (k a> 3 × 10 −4M). Isoproterenol-stimulated enzyme activity is blocked by propranolol (k i= 2.4 × 10 −9M, IPS 339 (k i= 4 × 10 −9M), H35/25 (k i = 1.2 × 10 −7M), atenolol (k i= 5.9 × 10 −6M) and practolol (k i= 1.8 × 10 −5M). These agonist and antagonist properties are quite similar to those demonstrated by β 2-adrenergic receptors and β 2-stimulated adenylate cyclase present in other tissues and indicate that the majority of adenylate cyclase-associated adrenergic receptors in cerebral microvessels are β 2. The findings are relevant to physiological studies of cerebral blood flow and vascular permeability.