Adrenergic Receptor Subtypes: Pharmacological Approaches

Abstract Although the existence of four distinct adrenergic receptor subtypes (α1, α2, β1, β2) has been recognized for more than 15 years, it has recently become clear that the adrenergic receptor family is much larger than previously suspected. Development of more selective agonists and antagonists and careful comparison of pharmacological properties have led to the realization that there are nine or more adrenergic receptor subtypes. Molecular cloning of many of these subtypes, discussed in an accompanying article, supports this conclusion. The adrenergic receptors fall into three major families (α1, α2, β) based on pharmacology, structure, and signal transduction, with at least three closely related members within each family. Here, we summarize the known pharmacological differences between these receptors and evaluate the best methods currently available for distinguishing these subtypes using selective drugs.