Potent Painkiller Found in Human Saliva

By Ed Edelson
HealthDay Reporter
Tuesday, November 14, 2006; 12:00 AM

TUESDAY, Nov. 14 (HealthDay News) -- French researchers say they've discovered a natural painkiller in human saliva that's several times more potent than morphine used in animal studies.

The researchers have named the pain inhibitor opiorphin, because it acts on the same pathways as morphine and other opiate painkillers. The finding could lead to improved pain medications because opiorphin is a naturally occurring molecule that is quickly metabolized, according to a report by researchers at the Pasteur Institute, in Paris.

Not much is known as yet about opiorphin, said study author Dr. Catherine Rougeot, director of the institute's Laboratory of Pharmacology of Neuroendocrine Regulation.

"We found it in saliva, that was the first step," she said. "Now, we are exploring its presence in other human biological tissues. Maybe it is localized in the blood, the brain. Now, I cannot answer."

It's not even known where in the body the substance is produced, Rougeot added. "We need more information to answer this question. Now, we need to characterize its function at physiological levels and learn by which tissues it is produced," she added.

The study was published in this week's issue of theProceedings of the National Academy of Sciences.

The discovery was made after the researchers identified a powerful pain-inhibiting molecule in rats. Their search for a similar molecule in humans turned up opiorphin. In rat studies, injections of 1 milligram of opiorphin per kilogram of body weight equaled the painkilling power of 3 to 6 milligrams of morphine per kilogram. Opiorphin was equally effective against chemical-induced inflammation and acute physical pain.

In addition to studying opiorphin, Rougeot and her colleagues plan to make and study variations of the original molecule. "It is important to mimic such compounds," she said.

A painkiller arising from the research could have important applications for human use, Rougeot said. "Opiorphin is natural, so it is quickly metabolized," she said, so its effects on the body would be more limited than those of existing painkillers.

Rougeot already has contacted a pharmaceutical company about funding for more research on opiorphin. "To complete this program, I need very much money," she explained.

Identification of opiorphin is "a potentially very significant finding," said Dr. Max Kelz, an assistant professor of anesthesiology and critical care at the University of Pennsylvania. "This new compound could serve as a potentially useful therapy for fighting pain in a number of conditions."

Kelz agreed that the discovery was just a beginning. "More has to be done to elucidate how this affects other endogenous painkillers," he said. "But the results are certainly promising."

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