Radioligand Binding Assay for an Exon 11-Associated Mu Opioid Receptor Target.

Receptor binding provides a valuable approach for characterization of drugs and their receptors. There are three major families of opioid receptors: mu, delta, and kappa. Highly selective radioligands are available for all three classes of traditional receptors. Of the three, the mu receptor undergoes extensive alternative splicing, generating a number of traditional mu receptor subtypes as well as a nontraditional, truncated set of variants associated with exon 11. These exon 11-associated truncated variants are not readily labeled with current radioligands. Here we describe the synthesis of a radioiodinated ligand suitable for carrying out binding studies for this target.