Solution may be imminent for pain sufferers sensitive to morphine, study says

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Pain management in the long-term care setting can be especially challenging for residents whose pain is worsened by morphine. A recently published study sheds light on this phenomenon and provides some hope that these individuals can one day be treated with the potentially powerful opiate.

A team of Canadian, American and Italian researchers identified receptors in spinal cord cells known as microglia, which when activated by morphine, can in some cases cause pain. The effect can potentially be mitigated by regulation of a protein molecule – KCC2 – that is involved in transmitting sensory signals to the brain.

"Our discovery could have a major impact on individuals with various types of intractable pain, such as that associated with cancer or nerve damage, who have stopped morphine or other opiate medications because of pain hypersensitivity," said study co-author Michael Salter, M.D., Ph.D., senior scientist in the Neurosciences & Mental Health Program at The Hospital for Sick Children Research Institute in Toronto.

The researchers also determined that the physiological process that causes morphine-induced pain is separate from the process that leads to morphine tolerance, contrary to previous hypotheses.

The study was published in the online edition of the journal Nature Neuroscience.