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Acupuncture Releases Natural Painkiller

2010年5月31日下午05:30:00

When they get acupuncture, mice release a natural pain-relieving

molecule that scientists have never linked with the treatment before.

While it’s not clear yet whether the finding will apply to humans,

unraveling the biological secrets of acupuncture could help the

therapy become a mainstream way to tackle pain.

“I think it’s important that the Western world take acupuncture

seriously,” said Maiken Nedergaard, a neuroscientist at the University

of Rochester in New York. “Many patients have unnecessary pain. I hope

this can improve pain treatment.”

Acupuncture has been around for thousands of years, and the World

Health Organization has endorsed it for more than 20 conditions, but

Western medicine continues to be skeptical about the practice.

For managing pain, sessions last about 30 minutes and involve

inserting small needles into specific acupuncture points, then

periodically rotating the needles, using electrical stimulation or

adding heat.

Studies have shown a clear link between acupuncture and pain relief in

animals, but research on people has offered more confusing results,

said Richard Harris, who studies chronic pain and acupuncture at the

University of Michigan, Ann Arbor. Many large trials have found that

pretend acupuncture works just as well as -- and sometimes even better

than -- real acupuncture.

“The acupuncture community feels that acupuncture is doing something,

but differentiating that from the effects of sham acupuncture is more

difficult to do,” Harris said, partly because pain is so complicated

in people, and the placebo effect is powerful.

“When a patient complains of chronic pain, there’s not just the

intensity of painful stimulation,” Harris said. “There are also

issues about whether the person can still work and provide for their

family, whether there is a disability or they are under litigation to

receive money to compensate them for their illness. A lot of factors

go into pain.”

In his own studies, Harris and his group have found that sham

acupuncture works by increasing levels of endorphins and other feel-

good chemicals in the brain, while true acupuncture works by targeting

the receptors for those chemicals, increasing the number of receptors

that are activated or helping them bind more tightly.

Still other studies have shown that certain parts of the brain get

turned off during acupuncture therapy, leading to analgesic effects.

In the new study, just published in the journal Nature Neuroscience,

Nedergaard and colleagues looked instead at adenosine, a molecule that

influences inflammation, sleep and the heart, and also acts as a

natural painkiller. Using mice with injured paws, the scientists first

demonstrated that adenosine was released during acupuncture.

Next, they found that acupuncture reduced the amount of pain that the

mice felt by two-thirds. The researchers measured pain levels by how

quickly the animals moved their legs away when touched. In mice that

didn’t have adenosine receptors and so couldn’t benefit from any of

the molecule’s effects, there was no relief from pain.

Finally, the researchers gave the mice an approved leukemia drug that

lengthens the amount of time that adenosine sticks around. With the

drug, the animals experienced relief for three times as long: three

hours instead of an hour.

If the same strategy worked in people, it might be possible to treat

chronic pain more effectively with, say, a combination of acupuncture

and drugs that enhance acupuncture’s benefits. One hope is that

acupuncture could cut into the amount of medicine people need to take,

Nedergaard said. That could reduce side effects and lower the chances

of addiction to narcotics.

That’s a big if, Harris warned. These kinds of pain studies in rodents

often don’t translate to humans, and the new study didn’t compare

needle pricks at specific acupuncture points with pricks in other areas.

Still, he said, by pinpointing the science of how acupuncture works,

studies like this give legitimacy to acupuncture and help move the

field forward.

“There are definitely people out there that are suffering from chronic

pain that could get better if they had access to treatment and if

their insurance companies covered it,” Harris said. “I really do

think that acupuncture offers hope for some people.”