( Why do so many people continue to suff...)Old memory traces in brain may trigger chronic pain

Why do so many people continue to suffer from life-altering, chronic pain long after their injuries have actually healed"

The definitive answer -- and an effective treatment -- has long eluded scientists. Traditional analgesic drugs, such as aspirin and morphine derivatives, haven’t worked very well.

A Northwestern University researcher has found a key source of chronic pain appears to be an old memory trace that essentially gets stuck in the prefrontal cortex, the site of emotion and learning. The brain seems to remember the injury as if it were fresh and can’t forget it.

With new understanding of the pain source, Vania Apkarian, professor of physiology, and of anesthesiology, at Northwestern’s Feinberg School of Medicine, has identified a drug that controls persistent nerve pain by targeting the part of the brain that experiences the emotional suffering of pain. The drug is D-Cycloserine, which has been used to treat phobic behavior over the past decade.

In animal studies, D-Cycloserine appeared to significantly diminish the emotional suffering from pain as well as reduce the sensitivity of the formerly injured site. It also controlled nerve pain resulting from chemotherapy, noted Apkarian, who is a member of the Robert H. Lurie Comprehensive Cancer Center at Northwestern University.

The drug has long-term benefits. Animals appeared to be pain free 30 days after the last dose of a 30-day regime of D-Cycloserine.

The study, funded by the National Institutes of Health, will be published in the journal Pain this fall. (It has been published on-line.)

“In some ways, you can think of chronic pain as the inability to turn off the memory of the pain,” Apkarian said. “What’s exciting is that we now may be relieving what has clinically been the most difficult to treat—the suffering or the emotional component of pain.”

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Source:Northwestern University