This is a classic article from New Scientist’s archive, republished as part of our 50th anniversary celebrations

MORPHINE and its related family, the opiates, interact strongly with molecular receptors in specific areas of the brain. Presumably the brain didn’t design a complex system such as this simply for the convenience of the products of poppy seeds. So why does the interaction happen? It now appears that the opiates are mimicking the action of a chemical normally produced in the brain – an endogenous opiate. This substance – which has been called enkephalin because of its origin in the brain – …