Adrenoceptors as models for G protein-coupled receptors: structure, function and regulation.

Catecholamines, either endogenous hormones or a variety of exogenous synthetic pharmacological agents, bind to adrenoceptors to mediate their ultimate clinical effects [21]. Since adrenoceptors mediate many cardiovascular responses, pharmacological stimulation and inhibition of adrenoceptors may be useful to the anaesthetist. Ahlquist described originally two adrenoceptor subtypes (alpha and beta) in 1948 [1], but for many years four "classic" adrenoceptor subtypes (alpha13 alpha2, beta! and beta2) have guided our understanding of human physiological responses and clinical administration of catecholamine drugs. Recently, genes encoding nine distinct adrenoceptor subtypes (alpha^, alpha1B, alphalc, alpha2C2, alpha2C43 alpha2C10, beta13 beta2 and beta3), have been discovered. The elucidation of new adrenoceptor subtypes has already facilitated the search for, and development of, adrenoceptor subtype selective agonists and antagonists.