Abstract
Evidence is presented that the receptors responsible for the mediation of analgesia by morphine-like drugs are similar to those which are involved in the production of a reversible lenticular opacity. The activity of a number of compounds in mice on the lens was closely correlated with analgesic potency in this species. Stereospecificity for isomers with d configuration was demonstrated for both effects. Nalorphine only antagonized the lenticular opacity activity of those drugs the analgesic action of which it abolished.