Acupuncture is effective at relieving pain.
Acupuncture works by stimulating a natural painkiller in the body that swells arteries and allows more blood to flow through, scientists have discovered. The identification of the chemical adenosine as a central player could also make the ancient Chinese therapy even more effective at relieving pain.
Scientists were able to triple the beneficial effects of simply sticking needles in mice by adding a leukaemia medication that increased their amounts of the molecule.
Dr Maiken Nedergaard, a neuroscientist at the University of Rochester, New York, said: “Acupuncture has been a mainstay of medical treatment in certain parts of the world for 4,000 years, but because it has not been understood completely, many people have remained sceptical.
“In this work, we provide information about one physical mechanism through which acupuncture reduces pain in the body.
“What we found is that adenosine, a natural pain killer, is released during acupuncture and that adenosine may be the primary way acupuncture reduces pain.
“The most important observation is that acupuncture worked almost three times as long if we gave a drug that slow down the removal of adenosine.”
Adenosine, which also helps to regulate sleep and keep the heart healthy, becomes active in the skin after an injury to inhibit nerve signals and ease pain.
The researchers, whose findings are published in Nature Neuroscience, performed acupuncture treatments on mice that had discomfort in one paw, giving them each a thirty minute acupuncture treatment near the knee, with very fine needles rotated gently every five minutes, much as is done in standard acupuncture treatments with people.
In mice with normal functioning levels of adenosine, acupuncture reduced discomfort by two-thirds, while in those engineered not to produce the chemical it had no effect.
And when adenosine was turned on in the tissues, discomfort was reduced even without acupuncture.
During and immediately after an acupuncture treatment, the level of adenosine in the tissues near the needles was 24 times greater than before.
Once the scientists recognised adenosine’s role, the team explored the effects of a cancer drug called deoxycoformycin, which makes it harder for the tissue to remove it.
The compound boosted the effects of acupuncture treatment dramatically, nearly tripling the accumulation of adenosine in the muscles and more than tripling the length of time the treatment was effective.
Dr Josephine Briggs, director of the National Centre for Complementary and Alternative Medicine at the National Institutes of Health in the US, said: “It is clear that acupuncture may activate a number of different mechanisms.
“This carefully performed study identifies adenosine as a new player in the process. It is an interesting contribution to our growing understanding of the complex intervention which is acupuncture.”