When D-Cycloserine, which has also been used recently to treat phobic behavior, was injected into the medial prefrontal cortex of the brain, rats responded with a reduction in chronic pain. However, when the researchers injected the medicine into other portions of the brain, the rats did not response to the pain.

The Apkarian team reasoned that the medial prefrontal cortex involves the emotional responses to chronic pain, which is why D-Cycloserine had a positive affect on chronic pain but did not have an affect when injected in other areas of the brain. The drug seems to reduce the emotional suffering from pain and to diminish the sensitivity of the injury.

Apkarian states: "In some ways, you can think of chronic pain as the inability to turn off the memory of the pain. 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."

Previous research by the Apkarian team found that the medial prefrontal cortex is more active when patients have chronic pain than when they do not experience such pain. According to the Science News article “TB medication offers pain relief” (August 4, 2007, page 77), “… this supports their theory that learned emotional responses centered in the medial prefrontal cortex play a key role in the experience of chronic, or neuropathic, pain.”

The journal article by Apkarian and his team of researchers will be published in a future issue of the journal Pain. Their next step is to test the drug on humans to determine if the source of chronic pain is indeed within the brain’s prefrontal cortex, which is the location of emotions and learning. The researchers contend that this part of the brain remembers the injury. Now, they must learn why the brain cannot forget the chronic pain from an injury and how to counter it.


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