The human body produces a natural painkiller several times more potent than morphine, research suggests.
When given to rats, the chemical, called opiorphin, was able to curb pain at much lower concentration than the powerful painkiller morphine.
The French team said their findings could be lead to new pain treatments.
But other scientists were unsure of the significance of the work, which is published in the Proceedings of the National Academy of Sciences.
Source - BBC News