Adrenergic Receptor
Adrenergic receptors are Class A GPCRs that bind the catecholamines epinephrine and norepinephrine, translating sympathetic nervous system input into cellular responses. The nine human subtypes divide into α1 (Gq-coupled, promoting phospholipase C signaling and smooth muscle contraction), α2 (Gi-coupled, inhibiting adenylyl cyclase and acting as presynaptic autoreceptors) and β1-β3 (predominantly Gs-coupled, raising cAMP and stimulating cardiac output, bronchodilation and lipolysis). This receptor class ranks among the most heavily exploited drug targets in medicine: β-adrenergic antagonists manage hypertension and heart disease, β2 agonists such as salbutamol relieve asthma, and α2 agonists like clonidine act as antihypertensives and sedatives.
