?1 Adrenoceptor subtypes: A synopsis of their pharmacology and molecular biology

Pharmacological and molecular biological studies have revealed heterogeneity among α1 adrenoceptor subtypes. Pharmacological agents used to characterize these sites often possess only moderate selectivity for a particular α1 adrenoceptor or have effects on other adrenergic or nonadrenergic receptors. Cloning studies have identified distinct amino acid sequences for three subtypes of α1 adrenoceptor, although the pharmacological characteristics of expressed receptors did not always coincide with expectations. As a result, controversial and alternate classification concepts have emerged that propose different numbers of α1 adrenoceptors or different naming conventions. Recent advances with an increasing variety of more selective compounds have resulted in an emerging consensus that identifies three subtypes of α1 adrenoceptor. The pharmacological and molecular biological studies that have contributed to or promoted resolution of these controversies are discussed in this review. Drug Dev. Res. 39:54–107.