The adrenoceptors (adrenergic receptors) are targets for the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). These receptors are widespread in the body and binding of catecholamines produces a sympathetic response ('flight-or-fight response') resulting in increased heart rate, pupil dilation and energy mobilization amongst other responses. There are three major types of adrenoceptor, alpha1, alpha2 and beta. Each type is thought to have three subtypes; alpha1 (1A,1B,1D), alpha2 (2A,2B,2C) and beta (1,2,3) (Bylund DB et al, 1994).
Ruffolo RR, Jr,