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ALBUQUERQUE, N.M. - Doctors at the University of New Mexico don't have to feel their patients' pain anymore. They can see it.

Physicians at the university's MIND Imaging Center have discovered that the brain releases a noticeable amount of two chemicals when it experiences pain.

That knowledge could turn what has been a subjective problem for patients into an objective science in which pain is measurable, said Paul Mullins, who directs studies of the phenomenon.

"When there are no physical signs of pain, it's very hard for patients to get any sort of acceptance from doctors," Mullins said. "We sort of stumbled on this new way of actually seeing pain." Mullins and co-investigator Wilmer Sibbitt finished their first yearlong study of the phenomenon about a month ago at the MIND center, which stands for Mental Illness and Neuroscience Discovery.

"Pain is interesting because the reaction to it differs from person to person," Sibbitt said. "You can put an adverse stimulus on two different people, and one will say there's almost no pain, and the other will be in agony."

The doctors stumbled onto the phenomenon when a researcher's ear got pinched during a brain scan, Mullins said.

"We had a subject in the scanner for a totally different study, and her ear was pinned down by a pair of headphones," Mullins said. "She knew if she moved it would invalidate the results so she stayed still. When it was over she told us she was in a lot of pain, and it might invalidate the results, but we thought it was interesting and looked for changes in brain patterns."

The pain had triggered a large release of the related chemicals glutamine and glutamate, which help nerves send signals through the brain.

"All of a sudden out of that there became a new way to study pain," Sibbitt said. "It's fascinating that there can be such large neurochemical changes involved, and we can actually measure them." Scans of the two chemicals will help doctors study painful diseases more closely and could lead to better pain-fighting techniques, Sibbitt said.

"We can look at more common pain syndromes, like fibromyalgia, which is a hypersensitivity to pain," Sibbitt said. "Patients with that problem have a horrible time and often have to stop working. Nobody knows what causes it, and I think it's very likely a brain disorder. This technique could help us know that with more certainty." Mullins has applied for a $275,000 National Institutes of Health grant to study the effect in fibromyalgia patients, he said.

"Pain can cause lack of sleep, social problems and in some cases even a reduction in brain matter if it persists for a long time," Mullins said. "Glutamine is released normally by the brain, but if too much of it is released for too long it becomes toxic. I theorize that might be a factor in chronic pain and many of these diseases."

The method could also help pharmaceutical companies develop better drugs to treat pain and study how drugs, diet and exercise work to fight it, Sibbitt said.

"There are a lot of avenues to explore," Mullins said. "Other people have been looking for something like this, but we're the first to actually find it. We want to continue working on it and studying chronic pain populations so we can understand what's going on and hopefully help those people more effectively."