High-tech images of the brains of chronic pain sufferers have found that the ancient practice of acupuncture fights pain by making key brain cells more sensitive to the pain-dampening effects of opioid chemicals. The study, published online in the August issue of the journal NeuroImage, comes less than a year after the publication of a controversial study that concluded acupuncture was no more effective than sham treatment at reducing pain.
Researchers at the University of Michigan's Chronic Pain and Fatigue Research Center used a positron emission tomography (PET) scanner to view the brains of 20 women diagnosed with fibromyalgia who reported suffering nerve and muscle pain at least 50% of the time. The PET scans were conducted during each woman's first acupuncture session and, a month later, her eighth.
In the regions of the brain that process and dampen pain signals -- the amygdala, caudate, cingula, thalamus and insula -- the PET scans showed an increase in the receptivity -- and possibly the number -- of brain cells to which opioid substances bind. Study author Richard E. Harris said that suggests that acupuncture appears to make the body more responsive to opioid painkillers.
But the mainstay of traditional Chinese medicine also appears to enhance the body's ability to regulate pain naturally, Harris said. Many of the analgesic chemicals the body produces, including endorphins (the source of what endurance athletes call "the runner's high") and enkephalins (which act to tamp down the sensation of pain), also bind to the opioid receptors. So if acupuncture treatments enhance those chemicals' ability to find a receptor to bind to, these natural painkillers work better as well.
Harris, a molecular and cell biologist at the University of Michigan and a licensed acupuncturist, said the group's findings are consistent with research that has found patients treated with acupuncture before surgery often need less post-operative medication to manage their pain. The acupuncture in these cases may have the effect of sensitizing the brain's opioid receptors to medication, making it work better.
The study may even support the controversial earlier finding that sham acupuncture works as well as real acupuncture to reduce pain, but that the two work in to reduce pain in different ways. In that experiment, patients seemed to gain considerable pain relief merely by a procedure that inserted needles into the body randomly, as oppose to following the paths of energy meridians that guide needle placement in acupuncture.
The random sinking of needles through the skin may prompt the body to increase its production of pain-dampening endorphins and enkephalins, Harris surmised. True acupuncture may work differently: Its painkilling effect may come not from boosting the supply of circulating natural analgesics, but by improving the ability of those chemicals to dock at a brain cell and exert their painkilling effects.
While many patients may turn to acupuncture as an alternative to conventional medication, Harris said his group's study suggests that the two means of pain relief can complement each other.
"I don't see them as mutually exclusive, and in some cases, they may work synergistically," Harris said.
-- Melissa Healy