ABSTRACT
Since a drug acting at a receptor must bind to the receptor before exerting an effect, it may seem obvious that measuring directly the binding of radiolabeled drugs, alone and in combination with other drugs, would provide valuable pharmacological information. As recently as 15 years ago, however, radioligand-binding experiments, and the conclusions drawn from them, were regarded with deep suspicion by a large section of classic pharmacologists. There were good reasons for this, since binding assays often produced complex and unexpected results that were often interpreted, perhaps all too easily, as indicating the existence of receptor subtypes. Today, many of these complexities are understood, either as artifacts or as a true phenomena that contribute to our understanding of receptor transduction and heterogeneity, and radioligand-binding assays are now central to many drug discovery projects.
