Adrenergic and Cholinergic Receptors of Cerebral Microvessels

The presence of alpha- and beta-adrenergic and muscarinic cholinergic receptors in cerebral microvessels of the rat and pig was assessed by ligand binding techniques. The results demonstrate the presence of specific binding to alpha 2- and beta-adrenergic receptors but no appreciable specific binding to alpha 1-adrenergic or muscarinic cholinergic receptors. beta-Adrenergic receptors of pig cerebral microvessels are similar to those of the brain and other organs in their binding characteristics to the tritiated ligand and in their stereospecificity of binding to the biologically active isomers of beta-adrenergic agonists. Further evidence derived from the differential potency of binding displacement by the various beta-adrenergic agonists and selective beta 1- and beta 2-adrenergic antagonists indicates that beta-adrenergic receptors of pig cerebral microvessels are mostly of the beta 2-subtype.