Discrimination of narcotic drugs on 3H-fentanyl receptor binding.

Stereospecific opiate receptor binding was measured using specifically labeled fentanyl in the presence of an excess of either dextromoramide or levomoramide, only the former being the analgesic isomer. In a very large series of chemically related drugs, but of different pharmacological activity, it was possible to recognize compounds endowed with a potential morphine-like activity. Attempts were made to localize the opiate receptors within the neuronal cell.