WASHINGTON (Reuters) - A single gene can explain why injuries that spell mere discomfort for one person can mean agony for another, researchers said Tuesday.
The gene, found in animals ranging from mice to humans, also helps explain why some people get more relief than others from painkillers based on opium, they said.
The team, at Johns Hopkins University in Baltimore and the National Institute on Drug Abuse (NIDA), said the gene controls the mu opiate receptor, a molecule that helps the body's natural opiates enter cells.
And they said it shows that some people who seem sensitive to pain are not simply crybabies. ``People have long been skeptical that pain has a genetic basis,'' Dr. George Uhl of NIDA, who led the study, said in a statement.
``Many assume the way people respond is voluntary. 'Just put up with it' has been a common recommendation for years,'' Uhl added. ``But now people can think of pain as a genetically regulated problem.''
The same mu opiate receptor also bonds with morphine, which is derived from opium. That could help explain why some people respond better than others to opiate drugs, researchers said.
Such drugs, which include not only morphine but Percodan, Demerol and others, already are classified as mu-opioids.
But knowing even more about the genetic basis underlying pain responses could help doctors tailor drugs to work specifically for different people, Uhl said.
To learn more about the gene's effects, Uhl's team looked at eight different strains of mice, each of which possessed a slightly different version of the mu opiate receptor gene.
Those with more active versions of the gene had more receptors -- meaning their cells could absorb more opiates, natural or otherwise.
Mice bred to possess half the usual number of opiate receptors were much more sensitive to pain, Uhl and colleagues reported in the Proceedings of the National Academy of Sciences. Mice who had the gene ``knocked out'' so they had no receptors were even more sensitive, they said.
People possess the same gene, Uhl's team said.
They tested several volunteers and then looked at studies other researchers had conducted on people. As in mice, people have different variations of the gene, and other studies on pain have shown that some people have twice the number of mu receptors than other people.
``It's rare to find a gene where the animal evidence for its effect is so strong or has such a clear carry-over to human studies,'' Uhl said.
This page last updated on October 04, 2003 12:09 AM.
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