Adrenergic alpha₁-receptor (α₁-AR)

The **adrenergic alpha₁-receptor** is a membrane-bound G protein-coupled receptor (GPCR) that binds the endogenous catecholamines norepinephrine and epinephrine. Three highly homologous subtypes exist: α₁A-, α₁B-, and α₁D-adrenergic receptor, encoded by distinct genes and distributed in various tissues including blood vessels, heart, CNS, prostate, and smooth muscle. Activation of α₁-receptors exerts critical roles in vascular contraction, blood pressure regulation, cardiac adaptation, metabolic modulation, and central nervous system functions. These receptors are key targets for drugs used in treating hypertension, heart failure, benign prostatic hyperplasia, orthostatic hypotension, and congestion, among other conditions. Subtype-specific effects (e.g., α₁A for cardioprotection) have prompted research into selective drugs, though clinical agents commonly affect multiple subtypes.

Other names

Alpha-1 adrenergic receptorAlpha-1 adrenoceptorα₁-adrenergic receptorα₁A-, α₁B-, α₁D-adrenergic receptor (subtypes)

Agonists: Stimulate α₁-AR → activate Gq protein → phospholipase C activation → increased IP₃ and DAG → release of intracellular Ca²⁺ → smooth muscle contraction, vasoconstriction, increased heart contractility, metabolic effects. Antagonists (“blockers”): Inhibit α₁-AR → vasodilation, decreased blood pressure, relaxation of prostate and bladder smooth muscle. Inverse agonists: Stabilize the inactive state, reducing basal activity (example: cyclazosin).