Alpha-1 and alpha-2 adrenergic receptors (α1/α2-AR)

Alpha-1 and alpha-2 adrenergic receptors are a class of G protein-coupled receptors (GPCRs) that mediate the physiological responses to the catecholamines norepinephrine and epinephrine (StatPearls, 2023). Alpha-1 receptors, which include the 1A, 1B, and 1D subtypes, are primarily coupled to Gq proteins; their activation leads to the stimulation of phospholipase C, resulting in increased intracellular calcium and subsequent smooth muscle contraction in the vasculature and prostate (UniProt P35348). Alpha-2 receptors, comprising the 2A, 2B, and 2C subtypes, are typically coupled to Gi proteins, which inhibit adenylyl cyclase and decrease cyclic AMP levels (UniProt P08913). These receptors often act as presynaptic autoreceptors, providing a negative feedback mechanism to inhibit further release of norepinephrine from sympathetic nerve terminals. Clinically, alpha-1 antagonists like prazosin and tamsulosin are used to treat hypertension and benign prostatic hyperplasia by inducing vasodilation and relaxing prostatic smooth muscle (PubMed, PMID: 28613461). Alpha-2 agonists, such as clonidine and dexmedetomidine, are employed for their antihypertensive, sedative, and analgesic effects, and are also used in the management of ADHD and glaucoma (PubChem CID 2803). Non-selective alpha blockers, such as phentolamine, are critical in managing hypertensive emergencies associated with catecholamine excess, such as pheochromocytoma (StatPearls, 2023).

Other names

Alpha-adrenoceptorsAlpha-adrenergic receptorsADRA1ADRA2

Alpha-1 adrenergic receptor agonism (Gq-mediated phospholipase C activation), Alpha-1 adrenergic receptor antagonism, Alpha-2 adrenergic receptor agonism (Gi-mediated adenylyl cyclase inhibition), Alpha-2 adrenergic receptor antagonism.