[Adrenergic receptors--nomenclature and classification of the types and subtypes]

The purpose of this review is to present current knowledge regarding adrenergic receptors and their subtypes. These receptors belong to the superfamily of structures with seven transmembrane domains. They are coupled with G-regulatory proteins. Similarly to other membrane receptors, their division is based on three criteria: structural, transductional, and operational. At present, adrenergic receptors are divided into three main groups, depicted as alpha 1, alpha 2 a beta receptors. Receptors alpha 1 and alpha 2 are further divided into additional 4 subtypes, which are marked with upper case subscripts A-D. Receptors beta are subdivided into three types, marked with subscripts 1-3. Classification of adrenergic receptors can be considered as a prototype for classification of other membrane receptors. The significance of all known receptors subtypes is not yet known. Multiple subtypes of adrenergic and also other receptor types exist simultaneously not only in one tissue but also frequently in a single cell where they can exert both synergistic as well as antagonistic effects. The discovery of functions and interactions of individual receptor subtypes represents a big challenge for future studies. Introduction of new selective agonists and antagonists not only helps to classify various receptor subtypes but it also has a big therapeutic potential.