Pain relief is a common function of acupuncture, but in the past people are not very clear about its scientific principles. A recent study in the U.S. concluded that acupuncture can prompt the body to release a natural painkilling substance, which can have a pain-relieving effect. In 2010, the British journal Nature Neuroscience published a report that researchers from the University of Rochester and other institutions in the United States discovered this principle through animal experiments. They performed acupuncture on the corresponding knee area of a lab rat with paw discomfort for about half an hour, and found that this led to the release of a substance called adenosine in the body of the lab rat, which has a natural pain-relieving effect and can reduce the pain of the lab rat. Tests showed that the amount of adenosine in the corresponding area after acupuncture was more than 24 times higher than before acupuncture. To further verify this finding, the researchers also used a drug that makes it difficult for the body to eliminate adenosine naturally on the lab rats. The results showed that the accumulation of adenosine in the body increased significantly after the use of this drug, and the effective time of acupuncture for pain relief was extended to more than three times. Dr. Nedergaard, who participated in the study, said that acupuncture has a long history of treatment, but because its principle of action has been less clear, many people are skeptical of acupuncture, and the current study reveals that there is indeed a scientific principle of acupuncture pain relief.