ENDING A QUEST that has engaged some of the most productive minds in pain research for two decades, researchers last month unveiled the genetic sequence of the molecular receptor for morphine.
With the sequence now published, experts are predicting a burgeoning of knowledge about the molecular mechanisms of pain and its concomitant mysteries of analgesia, tolerance, and addiction. It is also hoped that the discovery will facilitate the development and testing of new pain relievers that are more potent than morphine and have fewer undesirable effects.
Of the three major classes of opioid receptors—μ, δ, and κ—it is the μ receptor, named for morphine's initial letter, that has drawn the most attention from scientists. It is through this receptor on the surface of nerve cells, this gateway, that the body experiences the analgesic and euphoric effects of almighty morphine.
Although the μ receptor was first identified in the 1970s, no