The δ-Opioid Receptor: Molecular Pharmacology, Signal Transduction, and the Determination of Drug Efficacy

Although it was long thought that opioid drugs act on specific receptor sites, opioid receptors themselves were not identified until about 25 years ago ([Pert and Snyder, 1973][1]; [Simon et al., 1973][2];[Terenius, 1973][3]). Chemists and pharmacologists suspected the existence of multiple opioid