Morphine-Synthesizing Pathway Found In Mice

Mammals make their own morphine, a new study shows.

Scientists have known for decades that people excrete some morphine in their urine, but most people assumed that the pain-killing drug came from the diet or drug use. A new study shows that mice, and probably humans and other mammals, can make morphine from scratch.

“This paper now really shows that the whole pathway [to synthesize morphine] operates in the mouse,” says Heinz Floss, an emeritus biochemist at the University of Washington in Seattle who was not involved in the work. The study, published online the week of April 26 in the Proceedings of the National Academy of Sciences, also shows that the body rapidly uses up morphine’s building blocks by breaking them down or converting them to other chemicals, which helps explain why it has been difficult to determine whether people make the compound, says Floss.

No one yet knows why the body makes morphine, but researchers suspect it could be a natural painkiller or perhaps is used to help nerve cells communicate with each other. Where the morphine is made also remains a mystery.

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