Millions of people worldwide use acupuncture to ease a variety of painful conditions, but it’s still not clear how the ancient treatment works. Now a new study of mice shows that insertion of an acupuncture needle activates nearby pain-suppressing receptors. What’s more, a compound that boosts the response of those receptors increases pain relief—a finding that could one day lead to drugs that enhance the effectiveness of acupuncture in people.
Researchers have developed two hypotheses for how acupuncture relieves pain. One holds that the needle stimulates pain-sensing nerves, which trigger the brain to release opiumlike compounds called endorphins that circulate in the body. The other holds that acupuncture works through a placebo effect, in which the patient's thinking releases endorphins. Neuroscientist Maiken Nedergaard of the University of Rochester Medical Center in New York state was skeptical about both hypotheses because acupuncture doesn’t hurt and often works only when needles are inserted near the sore site. Nedergaard instead suspected that when acupuncturists insert and rotate needles, they cause minor damage to the tissue, which releases a compound called adenosine that acts as a local pain reliever.