Hans W. Kosterlitz (1903–1998), Solomon H. Snyder (b. 1938)
APPLYING RECEPTOR THEORY TO DRUG DEVELOPMENT. No drug is a more effective pain reliever than morphine, but scientists have long sought drugs that relieve pain as effectively without the potential for abuse. In 1973, results from Solomon Snyder’s laboratory at Johns Hopkins University confirmed the suspicion that morphine and other morphine-related drugs relieved pain, diarrhea, and other common ailments by interacting with specialized receptors in the brain and elsewhere. Observations of the antagonistic effects of naloxone (Narcan), a highly specific and selective morphine blocker, strengthened the argument. The all-inclusive term opioid was used to classify both drugs that have effects like morphine and their antagonists and that act at this receptor.
Why should the body expend valuable resources producing these complex protein receptors unless they were present to interact with endogenous compounds (compounds produced within the body)? In 1975, Hans Kosterlitz and John Hughes, at the University of Aberdeen, isolated small peptides (proteins) from human and other mammalian brains that interact with opioid receptors and are blocked by naloxone. These enkephalins and related endorphins—collectively, endogenous opioid peptides—are thought to play a role in pain and mood. Moreover, multiple types of opioid receptors (mu, delta, kappa) are found in the brain, spinal cord, and gastrointestinal tract and are responsible for the multiple opioid actions, including their addiction potential.
Now knowing that morphine’s pain-relieving effects and abuse potential result from its action at the mu receptor, scientists have developed drugs with complex actions at both mu and kappa receptors that are less likely to be abused. These include Buprenex, Stadol, and Talwin. The search for a totally abuse-free morphine continues.
Morphine and related natural drugs were not always classified as opioids. Since their effects were accompanied by sleepiness and stupor, they were called narcotics. With many newer semisynthetic derivatives, including heroin, Dilaudid, and OxyContin, scientists now use the all-inclusive term opioid to classify all drugs that act at the opioid receptors.
SEE ALSO Opium (c. 2500 BCE), Alkaloids (1806), Morphine (1806), Codeine (1832), Heroin (1898), Drug Receptors (1905), Methadone (1947), Fentanyl (1968), OxyContin (1996).
Originating in China more than 2,500 years ago, acupuncture is among the oldest and most commonly used medical practices in the world. It is thought to stimulate the central nervous system, releasing endogenous opioids that reduce pain.