History Opioid peptides in the brain were first discovered in 1973 by investigators at the University of Aberdeen, John Hughes and Hans Kosterlitz. They isolated "enkephalins" (from the Greek ) from pig brain, identified as Met-enkephalin and Leu-enkephalin. This came after the discovery of a receptor that was proposed to produce the pain-relieving analgesic effects of morphine and other opioids, which led Kosterlitz and Hughes to their discovery of the endogenous opioid ligands. Research during this time was focused on the search for a painkiller that did not have the addictive character or overdose risk of morphine.
History Opioid peptides in the brain were first discovered in 1973 by investigators at the University of Aberdeen, John Hughes and Hans Kosterlitz. They isolated "enkephalins" (from the Greek ) from pig brain, identified as Met-enkephalin and Leu-enkephalin. This came after the discovery of a receptor that was proposed to produce the pain-relieving analgesic effects of morphine and other opioids which led Kosterlitz and Hughes to their discovery of the endogenous opioid ligands. Research during this time was focused on the search for a painkiller that did not have the addictiv,e character or overdose risk of morphine.