Alpha-1 adrenergic receptor (α1-AR) (α1-AR)

Alpha-1 adrenergic receptors (α1-ARs) are a class of G protein-coupled receptors (GPCRs) primarily located on vascular smooth muscle, where they play a critical role in regulating systemic vascular resistance and blood pressure [1, 2, 5]. Upon activation by endogenous catecholamines like norepinephrine and epinephrine, these receptors couple with Gq proteins to trigger a signaling cascade involving phospholipase C, which increases intracellular calcium levels and leads to smooth muscle contraction, resulting in vasoconstriction [2, 6, 13]. The α1-AR family consists of three highly homologous subtypes—α1A, α1B, and α1D—each with varying distributions across different vascular beds and tissues [3, 4, 5]. In clinical practice, α1-AR agonists such as phenylephrine and norepinephrine are utilized to treat hypotensive states and shock by inducing vasoconstriction [7, 15, 17]. Conversely, α1-AR antagonists like prazosin, doxazosin, and tamsulosin are employed to manage hypertension and benign prostatic hyperplasia (BPH) by promoting vasodilation and relaxing prostatic smooth muscle [8, 14, 16]. Therapeutic targeting of these receptors requires careful management of side effects, most notably orthostatic hypotension and reflex tachycardia, which result from the potent effects of these drugs on vascular tone [8, 10, 16].

Other names

Adrenoceptor alpha 1Alpha-1 adrenoceptorAlpha-1 adrenoreceptorα1-adrenoceptor

Alpha-1 adrenergic receptors are Gq protein-coupled receptors [5, 6]. Activation by agonists leads to the activation of phospholipase C (PLC), which cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG) [2, 6, 13]. IP3 triggers the release of calcium from the sarcoplasmic reticulum, while DAG activates protein kinase C (PKC) [2, 6]. The resulting increase in intracellular calcium concentration promotes the formation of the calcium-calmodulin complex, activating myosin light chain kinase (MLCK) and leading to smooth muscle contraction and vasoconstriction [2, 6, 10].