Scientists Reveal How Morphine May Increase Pain
As many of us know, morphine is a narcotic drug that is used to treat moderate to severe pain. In some instances though, morphine tends to aggravate the pain rather than minimise it. If you’re one of those people whose pain gets worse when treated with this drug, scientists have good news for you. In a new study published in the journal Nature Neuroscience, Canadian researchers have successfully found why morphine may intensify pain.
"When morphine doesn’t reduce pain adequately the tendency is to increase the dosage”, says Dr. Michael Salter – senior Scientist and Head of Neurosciences & Mental Health at SickKids, Professor of Physiology at University of Toronto, and Canada Research Chair in Neuroplasticity and Pain. But sometimes, increasing morphine dosage can make the pain worse, he adds. In their study, Dr Salter and his team determined the molecular pathway by which morphine increases pain. They found that cellular and signalling processes for morphine tolerance are very different from those of morphine-induced pain. This is in conflict with the belief that drug tolerance and hypersensitivity are different results of similar response.
Speaking of the molecular pathway, the team identified a group of specialised cells (known as microglia) found in the spinal cord. According to the researchers, the microglia is the culprit behind morphine-induced pain hypersensitivity.
“When morphine acts on certain receptors in microglia, it triggers the cascade of events that ultimately increase, rather than decrease, activity of the pain-transmitting nerve cells."
The team also identified another molecule, a protein called KCC2, which is in charge of regulating the transport of chloride ions and the control of sensory signals to the brain. Dr Salter said morphine inhibits the activity of such protein, resulting to abnormal pain perception.
Currently, the team is researching on restoring the activity of the normal KCC2 to potentially prevent hypersensitivity.
Pain is a debilitating condition that affects the quality of life of many people. In Britain alone, over 10 billion people suffer from pain almost daily. Majority of sufferers had to take a day off from work because their pain is too intense to handle. Fortunately, there are other ways to address this condition when morphine and other pharmaceutical drugs don’t seem to work. Among the most popular ways to beat pain include acupuncture, herbal medicine, and massage.
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Source of this article:
Nature Neuroscience Journal Volume 16