A breakthrough means to ease pain for millions of patients has been discovered by US researchers – and it’s right inside our body.

Scientists at St. Louis University, Missouri, blocked a pain pathway in rodents using a receptor called A3, which is located in rats’ brains and spinal cords, and acts against intense feelings of discomfort.

The latest study was published in the medical journal, Brain.

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A3 is activated by adenosine, a native chemical stimulator, or synthetic drugs, and brings pain relief, or prevents pain.

“It has long been appreciated that harnessing the potent pain-killing effects of adenosine could provide a breakthrough step towards an effective treatment for chronic pain,” Daniela Salvemini, Professor of pharmacological and physiological sciences at the university, said, as quoted by the Daily Mail.

This new method of pain relief could prevent side effects existing in today’s pain-relief drugs: addiction and increasing tolerance. Other issues include “intolerable side effects that result in discontinued use, inadequate pain relief, and diminished quality of life."

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The existing drugs function via certain "pathways": circuits involving opioid, adrenergic, and calcium channels.

Should the finding prove successful, it could result in the development of breakthrough, non-addictive drugs for millions of pain sufferers.

“Our findings suggest that this goal may be achieved by focusing future work on the A3AR pathway, in particular, as its activation provides robust pain reduction across several types of pain,” Salvemini said.

Adenosine is also being examined as an anti-inflammatory and anti-cancer agent.