An international team of researchers has identified a brain area that works as a natural painkilling system and could pave the way for a possible alternative to opioids for the effective relief of chronic pain.

The findings showed that a single region of the prefrontal cortex, called the pregenual cingulate cortex, has a neuronal circuit and endogenous substances to modulate chronic pain. Stimulating this area that is important for endogenous analgesia -- the brain's intrinsic pain relief system -- could lead to the development of pain treatments that activate the painkilling system and cut down the dangerous side-effects of opioids. "We're trying to understand exactly what the endogenous analgesia system is: why we have it, how it works and where it is controlled in the brain," said lead author Ben Seymour from the University of Cambridge in Britain.

"If we can figure this out, it could lead to treatments that are much more selective in terms of how they treat pain," Seymour added. Opioid drugs hijack this endogenous analgesia system, which is what makes them such effective painkillers. However, they are also highly addictive and have now become the leading cause of death.

To identify where in the brain this system was activated, the team attached a metal probe to the arm of a series of healthy volunteers -- and heated it up to a level that was painful, but not enough to physically burn them. The volunteers then played a type of gambling game where they had to find which button on a small keypad cooled down the probe. The level of pain the volunteers experienced was related to how much information there was to learn in the task.

The results, published in the open access journal, eLife, showed why and how the brain decides to turn off pain in certain circumstances, and identify the pregenual cingulate cortex as a critical 'decision centre' controlling pain in the brain.