Alpha-1A and Alpha-2A adrenergic receptors (ADRA1A/ADRA2A)

The Alpha-1A and Alpha-2A adrenergic receptors are G protein-coupled receptors (GPCRs) that mediate the physiological effects of the catecholamines norepinephrine and epinephrine [1, 4, 15]. The Alpha-1A subtype (ADRA1A) primarily signals through the Gq protein, activating phospholipase C and increasing intracellular calcium, which leads to smooth muscle contraction in the vasculature and prostate [4, 7, 13]. The Alpha-2A subtype (ADRA2A) signals through the Gi protein, inhibiting adenylate cyclase and reducing cAMP levels, often acting as a presynaptic autoreceptor to inhibit further neurotransmitter release [12, 15, 16]. These receptors are critical therapeutic targets; Alpha-1A antagonists like tamsulosin are used to treat benign prostatic hyperplasia by relaxing prostatic smooth muscle, while Alpha-2A agonists like guanfacine and dexmedetomidine are used for ADHD and sedation, respectively [1, 12, 13]. Although often discussed together in the context of non-selective alpha-adrenergic ligands, they are distinct proteins encoded by different genes with contrasting signaling mechanisms [3, 14, 15]. This combined target designation is typically found in pharmacological network studies rather than as a single biological entity [6, 9, 11].

Other names

ADRA1AADRA2AAlpha-1A adrenoceptorAlpha-2A adrenoceptorAlpha-1A/2A adrenoceptorsAdrenoceptor alpha 1AAdrenoceptor alpha 2A

Alpha-1A adrenergic receptors couple to Gq proteins to activate phospholipase C, leading to IP3-mediated calcium release and smooth muscle contraction [4, 7, 13]. Alpha-2A adrenergic receptors couple to Gi proteins to inhibit adenylate cyclase, decreasing cAMP levels and inhibiting neurotransmitter release or modulating post-synaptic signaling [12, 15, 16].