Scientists at the University of Manchester have found that the number of opiate receptors in the brain increases to combat severe pain in people with arthritis.
It has long been known that we have receptors in our brains that respond to natural painkilling opiates such as endorphins, but the researchers in Manchester have shown for the first time that that these receptors increase in number to help cope with long-term pain.
By applying heat to the skin using a laser stimulator, Dr. Christopher Brown and colleagues demonstrated that the more opiate receptors there are in the brain, the higher the ability to withstand the pain. The study involved 17 patients with arthritis and nine healthy controls, and used Positron Emission Tomography (PET) imaging to show the spread of the opioid receptors.
According to the researchers, the increase in opiate receptors in the brain may be an adaptive response to chronic pain, allowing people to deal with it more easily.
“As far as we are aware, this is the first time that these changes have been associated with increased resilience to pain and shown to be adaptive,” said Dr. Brown. “Although the mechanisms of these adaptive changes are unknown, if we can understand how we can enhance them, we may find ways of naturally increasing resilience to pain without the side effects associated with many pain killing drugs.”
Professor Anthony Jones is director of the Manchester Pain Consortium, which focuses on improving the understanding and treatment of chronic pain. Welcoming the findings of the study, he said: “There is generally a rather negative and fatalistic view of chronic pain. This study shows that although the group as a whole are more physiologically vulnerable, the whole pain system is very flexible and that individuals can adaptively upregulate their resilience to pain.
“It may be that some simple interventions can further enhance this natural process, and designing smart molecules or simple non-drug interventions to do a similar thing is potentially attractive.”
The research has been published in the journal Pain.