Adrenoceptors (also called Adrenergic receptors) are the receptors for the catecholamines adrenaline and noradrenaline (called epinephrine and norepinephrine in the United States). Adrenaline and noradrenaline play important roles in the control of blood pressure, myocardial contractile rate and force, airway reactivity, and a variety of metabolic and central nervous system functions.The Adrenoceptors are members of the G-protein-coupled receptor (GPCR) superfamily of membrane proteins. They share a common structure of seven putative transmembrane domains, an extracellular amino terminus, and a cytoplasmic carboxyl terminus.TheAdrenoceptors are divided into three types: α1, α2 and β adrenoceptors. Each type is further divided into at least three subtypes: α1A, α1B, α1D, α2A, α2B, α2C, β1, β2, β3. 1,2They are expressed in nearly all peripheral tissues and in the central nervous system.