Potent Painkiller Found in Human Saliva
By Ed Edelson
HealthDay Reporter
posted: 14 November 2006
12:17 pm ET



(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 the Proceedings 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."

Dr. Ed Ross, director of the pain management center at Brigham and Women's Hospital in Boston, said opiorphin could be an important addition to the only other natural painkillers found in the human body -- endorphins.

"Endorphins have been around for quite a while, but they are weak and have a short half-life, so the problems in using them clinically are very significant," Ross said. "Now, this is a compound that has much more strength than the endorphins. It also suggests a potential for other synthetic compounds that work on different receptors that we have known before, and, for a pain doctor, that is very significant."

Another paper in the same issue of the journal described the discovery of toxins from two species of snails that hold promise for relief of severe nerve pain such as sciatica. The toxins lock onto nerve cell receptors to block nerve pain, said the report by researchers at the University of Utah.

One of the toxins, designated Vc1.1, is being developed by an Australian company and already is undergoing trials in human patients. It is administered by injection.

It may be possible to develop a version that could be taken orally, but that might require 10 years, said a statement by J. Michael McIntosh, a research professor of biology and a member of the team reporting the discovery.

"There really is no highly effective treatment available for this kind of severe pain, so having a new way to treat it is exciting," he said.

More information

For the latest on pain and its treatment, visit the U.S. National Library of Medicine.