Different types of analgesics and narcotic antagonists were examined by a variety of in vivo and in vitro techniques to discern their effect on the narcotic receptor. For example, heroin, 6-acetylmorphine, 3,6-diacetylnormorphine and 6-acetylnormorphine were tested in vivo, were examined on quinea-pig ileum, and their affinity for the receptor in rat brain homogenate was determined in an effort to find the mode of action of heroin on the narcotic receptor in vivo. Longer-acting narcotic agonists and antagonists were prepared, as were potential irreversible inhibitors of the narcotic receptor. Some of these compounds were tested using the above-mentioned animals and systems, in monkey species, and in an adenylate cyclase assay. Further, the relatively long-acting narcotic antagonists which were prepared gave insight into the molecular configuration of the narcotic receptor.