From today's Boston Globe:

Acupuncture can relieve pain, but how the ancient technique works is still something of a mystery. A new study in mice pinpoints a natural painkiller that may be a clue.

Dr. Maiken Nedergaard of the University of Rochester led a team that tested acupuncture in mice, inserting fine needles near their knees corresponding to points on human charts. The mice had inflamed paws and the researchers measured their pain response by seeing how long it took them to withdraw their sore paws from touch or heat. When the mice had the tiny needles inserted and moved around for 30 minutes, high levels of the neurotransmitter adenosine were released surrounding the needle points and their pain was reduced by two-thirds. Adenosine, which inhibits nerve cells in response to injury, acts like the local anesthetic lidocaine.

In mice genetically engineered not to produce adenosine, acupuncture did not ease their pain. And the researchers found that when they gave the mice a leukemia drug that slows down adenosine’s removal from tissue, the mice had pain relief three times as long as when they had the treatments without the drug.

Isolating adenosine as an important factor in acupunture’s effectiveness may lead to a better understanding not only of pain and acupuncture, but also of other treatments, such as chiropractic manipulation and massage, the researchers said. But with mice, researchers can rule out the placebo effect. People sometimes say they feel better after getting a sham treatment, perhaps because their hope of relief is so powerful, but that’s unlikely to be the case with mice, Nedergaard said.

BOTTOM LINE: In experiments with mice, acupuncture activated the release of adenosine, a molecule known as a natural painkiller.

CAUTIONS: Results found in mice do not necessarily apply in humans.

WHERE TO FIND IT: Nature Neuroscience, May 30

Byron Russell