Alpha-adrenergic receptor (α-AR) (α-AR)

Alpha-adrenergic receptors (α-ARs) are a major class of G protein-coupled receptors (GPCRs) that mediate the physiological responses to the catecholamines norepinephrine and epinephrine (StatPearls, 2023 [1]). They are divided into two main types: α1, which is primarily excitatory and located on postsynaptic smooth muscle cells, and α2, which is often inhibitory and located on presynaptic nerve terminals (UniProt, 2024 [2]). Activation of α1-receptors leads to vasoconstriction and smooth muscle contraction in the prostate and eye, while α2-receptor activation inhibits neurotransmitter release and reduces sympathetic outflow from the central nervous system (NCBI Bookshelf, 2023 [3]). These receptors are vital therapeutic targets for a variety of conditions; for instance, α1-antagonists like tamsulosin are used for benign prostatic hyperplasia, and α2-agonists like clonidine are used for hypertension and ADHD (PubMed, 2022 [4]). However, targeting these receptors requires careful management of side effects such as orthostatic hypotension for α1-blockers or sedation for α2-agonists (StatPearls, 2023 [5]).

Other names

Alpha-adrenoceptorAdrenoceptor alphaADRAα-adrenergic receptor

Alpha-1 adrenergic receptors primarily activate the Gq protein pathway, stimulating phospholipase C to produce IP3 and DAG, which increases intracellular calcium and leads to smooth muscle contraction. Alpha-2 adrenergic receptors primarily couple with Gi proteins to inhibit adenylyl cyclase, thereby decreasing cAMP levels and inhibiting the release of norepinephrine from presynaptic neurons (StatPearls, 2023 [1]; PubMed, 2022 [4]).