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Acupuncture may trigger natural painkillers

May 31, 2010

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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

Cutting sugary drinks cuts blood pressure, too

Sugar-sweetened beverages — soda, fruit drinks, lemonade, and punch — have been implicated in higher rates of obesity and diabetes. A new study suggests there may also be a link between sugary drinks and blood pressure.

Dr. Liwei Chen of Louisiana State University Health Science Center led a team that analyzed diet and blood pressure in 810 adults enrolled in a trial comparing different weight-loss methods. At the start, the participants either had or were close to having high blood pressure. On average they drank one 12-ounce sugar-sweetened serving each day. After 18 months, all the participants on average had cut their sweetened beverages by half a serving a day, but the people who had lowered it by one serving had also reduced the top number in their blood pressure by 1.8 and the bottom number by 1.1.

Even small declines in blood pressure have been tied to a lower risk of heart attack and stroke, the authors said, suggesting that cutting sugar may help improve cardiovascular health.

BOTTOM LINE: People who cut down on their sugar-sweetened beverages also reduced their blood pressure.

CAUTIONS: The study can’t prove that sugary drinks and blood pressure are related. Also, because the study included few Hispanics and Asians, the results might not apply to them.

WHAT’S NEXT: The researchers plan to study people who do not have high blood pressure.

WHERE TO FIND IT: Circulation: Journal of the American Heart Association, May 24


Elizabeth Cooney can be reached at

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