α adrenergic receptor

α-adrenergic receptors are seven-transmembrane G protein-coupled receptors activated by norepinephrine and epinephrine, and they divide into α1 and α2 receptor families^[1]. Mechanistically, α1A, α1B, and α1D receptors mediate contractile responses through Gq/11, inositol phosphate turnover, phospholipase C activation, Ca²⁺ release, and protein kinase C signaling^[1][2]. These pathways support smooth muscle contraction, vascular tone regulation, prostate and bladder-neck contraction, and context-dependent MAPK activation^[2][3]. Compared with α2A, α2B, and α2C receptors, which are linked to adenylate cyclase inhibition and prejunctional control, α1 receptors emphasize stimulatory contractile and growth-related signaling^[1]. Isoform distinction is experimentally important because human epicardial coronary arteries predominantly express functional α1D, whereas prostate biology and benign prostatic hyperplasia research emphasize α1A/α1L signaling^[4][5]. In disease models, epinephrine-Adra1 signaling promoted tau hyperphosphorylation and aggregation, while an Adra1 antagonist inhibited these tauopathy-associated changes^[6]. For experimental applications, subtype-selective antagonists, receptor knockout models, and agonist-stimulation systems help define receptor-specific signaling, tissue selectivity, and disease-relevant mechanisms^[2][5][6].