Alpha-1 adrenergic receptor

alpha-1 (α₁) adrenergic receptors are G protein-coupled receptors (GPCRs) associated with the G_q heterotrimeric G protein. α₁-adrenergic receptors are subdivided into three highly homologous subtypes, i.e., α_1A-, α_1B-, and α_1D-adrenergic receptor subtypes. There is no α_1C receptor. At one time, there was a subtype known as α_1C, but it was found to be identical to the previously discovered α_1A receptor subtype. To avoid confusion, naming was continued with the letter D. Catecholamines like norepinephrine (noradrenaline) and epinephrine (adrenaline) signal through the α₁-adrenergic receptors in the central and peripheral nervous systems. The crystal structure of the α_1B-adrenergic receptor subtype has been determined in complex with the inverse agonist (+)-cyclazosin.