Chronic pain could be a symptom of opioid addiction, according to a recent study involving mice. The study was published in the journal Science.
Chronic pain is pain lasting more than three months and beyond a recovery period of injury. It affects millions of Americans and often follows an acute injury like one suffered in a car accident or other traumatic event.
The body often releases natural opioid compounds that have an immediate pain relieving effect after acute pain starts. However, The Scientist reports that this pain-reducing system could also have negative effects.
Sensory neurologist Bradley Taylor with the University of Kentucky Medical Center and his colleagues wondered if the answer to chronic pain could lie with the body’s mechanisms for reducing pain in the first place.
To test the theory, Bloomberg notes that the researchers caused inflammation in the paws of several mice, allowed it to fade, then blocked the rodents’ opioid receptors to that natural painkillers wouldn’t work. The mice exhibited withdrawal-like behaviors, as well as pain and neural activity that indicated pain.
The symptoms were seen in the mice even six months after the initial injury. Taylor explained that there could be a battle between internal painkillers and the pain pathways, causing chronic pain. As the body becomes dependent on internal analgesics, the pain pathways become more sensitive.
Exploring pain pathways could help explain why people develop chronic pain. Taylor explained, “We thought the injury was producing activation of the pain pathways for much longer than previously thought. Instead, it’s possible the brain’s own natural opioids camouflaged the increased pain sensitivity.
Taylor added that stress and depression could play a role in developing chronic pain after a severe injury. Only about 10 to 20 percent of patients experience this. The researcher explained that stress and depression can interrupt the action of a key receptor that inhibits suffering.
Understanding the connection between the body’s natural pain signaling systems could help point to better therapies for patients with chronic pain.
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