Chronic pain sufferers have long bemoaned the fact that people often tell them the pain is “all in your head.” New research indicates that is partially true and it may be possible to ease chronic pain by erasing memories in the brain.
A team of researchers at McGill University in Montreal has found the key to understanding how memories of pain are stored in the brain. A protein called PKMzeta plays a critical role in building and maintaining memory by strengthening the connections between neurons. Researchers found that by blocking PKMzeta activity, they could reverse the hypersensitivity to pain that neurons develop. Erasing these painful memories reduces both persistent pain and heightened sensitivity to touch.
It’s long been known that the brain “remembers” painful experiences. Acute pain of even just a few minutes will leave a memory trace in the central nervous system. When there is new sensory input or feeling in the same area, the brain recalls the pain memory and magnifies the feeling, so that even a gentle touch can be agonizing. That is how normally protective acute pain turns into chronic pain.
“Perhaps the best example of a pain memory trace is found with phantom limb pain,” said McGill neuroscientist Terence 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 that is critical to the development of chronic pain. Until now, it was not known how pain memories were stored at the neuron level in the brain.
Coderre and his colleagues believe that further research on PKMzeta could lead to new methods to target the protein in pain pathways.
“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 McGill research is being published in the journal Molecular Pain