Adrenergic receptors (ARs) are members of the 7-transmembrane domain G-protein-coupled receptor superfamily that bind the endogenous catecholamines epinephrine and norepinephrine. Pharmacological, structural, and molecular cloning data indicate significant heterogeneity within this receptor family. Nine receptor subtypes have been identified thus far including three alpha-1 AR subtypes (1A/D, 1B, and 1C), three alpha-2 ARs (2A, 2B, and 2C), and three beta AR subtypes (1, 2, and 3). ARs participate in either the onset or maintenance of several disease states including hypertension, cardiac dysfunction (congestive heart failure, ischemia, arrhythmias), diabetes, glaucoma, depression, and impotence.
A2AR subtypes inhibit adenylyl cyclase, suppress voltage-sensitive calcium channels, and activate receptor-dependent potassium channels. All of the A2AR subtypes inhibit adenylyl cyclase through coupling to members of the Gi/Go class of G proteins. They are an essential component of the neural circuitry regulating cardiovascular physiology. The physiological function of the A2ARs in the kidney is to regulate sodium/hydrogen exchange although the role of A2AR subtypes remains to be precisely determined.