Alpha-1 adrenergic receptor; Alpha-2 adrenergic receptor (α1-adrenoceptor; α2-adrenoceptor)

Alpha-1 and alpha-2 adrenergic receptors are two major families of G protein-coupled receptors that mediate the physiological actions of catecholamines (epinephrine and norepinephrine) in the peripheral and central nervous systems through distinct signaling pathways. - Alpha-1 adrenergic receptors are primarily postsynaptic and mediate smooth muscle contraction, vasoconstriction, and increased blood pressure, with roles in cognition and metabolism. Subtypes include α1A, α1B, and α1D[2][4][5][6][10]. - Alpha-2 adrenergic receptors are found both pre- and postsynaptically, especially as inhibitory auto-receptors in the CNS and periphery, reducing norepinephrine release and sympathetic outflow. They have subtypes α2A, α2B, and α2C[2][3][10]. Both families are pharmacological targets for a range of drugs used in cardiovascular, neurological, and pain indications. They are membrane glycoproteins possessing seven transmembrane domains, coupling respectively to Gq proteins (α1) and Gi proteins (α2), and are distinguished by their tissue distribution, downstream signaling, and pharmacological profiles[1][2][3][6][8][9][10].

Other names

alpha-adrenergic receptorα1 receptorα2 receptoralpha-1 adrenoceptoralpha-2 adrenoceptoralpha-adrenoceptor

α1: Agonists cause vasoconstriction by activating Gq protein → increased IP3 and calcium signaling in smooth muscle α1 antagonists cause vasodilation by blocking this pathway α2: Agonists activate Gi protein, inhibit adenylate cyclase → reduced cAMP, inhibit norepinephrine release (presynaptic auto-receptor) α2 antagonists block inhibition, increasing norepinephrine release