Acupuncture -- using tiny needles in the skin to relieve pain -- really does change the way the brain manages pain, according to University of Michigan researchers.

They used brain scans to determine that acupuncture actually improves the functioning of receptors in the brain that can process and dampen pain signals, according to a news release on the work.

Painkillers, such as morphine, codeine and other medications are thought to work by binding to these opioid receptors in the brain and spinal cord.

Richard E. Harris, who wrote the study, said it could mean that patients with chronic pain could then get more benefit from those drugs.

Some large studies have shown that acupuncture is effective against pain, but they have also indicated that fake acupuncture also works, meaning that it could be that there is only a placebo effect.

"Interestingly both acupuncture and sham acupuncture groups had similar reductions in clinical pain," Harris said. "But the mechanisms leading to pain relief are distinctly different."

The study participants included 20 women who had been diagnosed with fibromyalgia, a chronic pain condition, for at least a year, and experienced pain at least 50 percent of the time. During the study they agreed not to take any new medications for their fibromyalgia pain.

The results appeared in the September Journal of NeuroImage.