Alpha-adrenergic receptors in the rat superior cervical ganglion.

α-Adrenergic receptor sites on membranes from rat superior cervical ganglia were measured by the specific binding of [³H]dihydroergocryptine, an α-adrenergic antagonist. The binding was specific, saturable, reversible, rapid, and stereoselective. Specific binding was displaced by α-adrenergic agonists in the expected order of potency and by α-adrenergic antagonists, but only weakly by a β-adrenergic agonist and antagonist. Decentralization of the ganglia by severing the preganglionic cholinergic nerve supply resulted in a marked decrease in the number of α-adrenergic receptors. The data suggest that about one-half the α-adrenergic receptors are located on the preganglionic cholinergic axon terminals and one-half on ganglionic cell membranes.