Multiple opioid receptors: ligand selectivity profiles and binding site signatures.

Methods are described for studying mu, delta, and kappa opioid binding sites, each without interference from the others. A large array of ligands has been characterized by ligand selectivity profiles, graphic depictions of affinities and selectivities. Binding site signatures have been derived, which uniquely describe each of the three types of sites. The mu, delta, and kappa binding sites have interesting common features and distinctive differences.