The science behind pain-memory may soon provide exciting new ways to treat chronic pain.

Chronic pain can terribly debilitating. For some individuals, the pain is so great that they can’t even bear to have clothes touch their skin. For others, it means that every step is a deliberate and agonizing choice. Whether the pain is caused by arthritic joints, an injury to a nerve or a disease like fibromyalgia, the latest research suggests there are new solutions for those who suffer from chronic pain.

A team of researchers led by McGill University neuroscientist Terence Coderre has found the key to understanding how memories of pain are stored in the brain. Amazingly – and more importantly – the researchers are also able to suggest how these memories can be erased, making it possible to ease chronic pain.

It has long been known that the our nervous system “remembers” painful experiences. In doing so, it leaves a memory trace of pain. And when there is new sensory input, the pain memory trace in the brain magnifies the feeling so that even a gentle touch can be excruciating.

Feeling Pain in a Foot That Isn’t There

“Perhaps the best example of a pain memory trace is found with phantom limb pain,” says Dr. Coderre. “Patients may have a limb amputated because of gangrene, and because the limb was painful before it was amputated, even though the limb is gone, the patients continue to feel they are suffering from pain in the absent limb. That’s because the brain remembers the pain. In fact, there’s evidence that any pain that lasts more than a few minutes will leave a trace in the nervous system.”

It’s this memory of pain – existing at the level of the neuron – that is critical to the development of chronic pain. But how these pain memories were stored at the neuron was unknown

Until now…

Recent work has shown that the protein, known as PKMzeta plays a crucial role in building and maintaining memory by strengthening the connections between neurons. Now Coderre and his colleagues have discovered that PKMzeta is also the key to understanding how the memory of pain is stored in the neurons. They were able to show that after painful stimulation, the level of PKMzeta increases persistently in the central nervous system (CNS).

Even more importantly, the researchers found that by blocking the activity of PKMzeta at the neuronal level, they could reverse the hypersensitivity to pain that neurons developed after irritating the skin by applying capsaicin – the active ingredient in hot peppers. They also found that erasing this pain memory trace was found to reduce both persistent pain and heightened sensitivity to touch.

Coderre and his colleagues believe that building on this study to devise ways to target PKMzeta in pain pathways could have a significant effect for patients with chronic pain. “Many pain medications target pain at the peripheral level, by reducing inflammation, or by activating analgesia systems in the brain to reduce the feeling of pain,” says Coderre. “This is the first time that we can foresee medications that will target an established pain memory trace as a way of reducing pain hypersensitivity. We believe it’s an avenue that may offer new hope to those suffering from chronic pain.”

The science of pain moves forward every day. Research like that being done at McGill University offers very real hope to those suffering with chronic and debilitating pain. 

February 18, 2012
The Healthy Mind Network 

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The above story contains original content and/or information reprinted and editorially adapted by The Healthy Mind. Material is provided by McGill University and EurekAlerts. 

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