A new painkilling substance has been discovered that is up to six times more potent than morphine when tested in rats — and it's produced naturally by the human body. Natural painkillers are very rare, and researchers hope that this recent find might be harnessed as a clinical treatment.
Naturally produced painkillers might help to avoid some of the side effects experienced by patients treated with synthetic compounds such as morphine, including addiction and tolerance with prolonged use. But the new substance will first have to be tested to confirm whether it will be an effective drug, experts warn.
The compound, dubbed opiorphin, seems to work by prolonging the body's own defences against pain, explain Catherine Rougeot of the Pasteur Institute in Paris, France, and her colleagues, who report the discovery in Proceedings of the National Academy of Sciences. It does so by preventing the breakdown of chemicals called enkephalins, which in turn activate opiate receptors that block pain signals from reaching the brain.
Rougeot's team tracked down the new compound after previously finding a similar natural painkiller in rats, called sialorphin. They wondered whether humans might produce something similar — and by analysing saliva samples, hit upon opiorphin.
This is the first natural substance to be found in humans that exploits this mechanism to relieve pain. But it's unlikely that opiorphin ordinarily has a painkilling role in the body, says Alistair Corbett, a specialist on opioids at Glasgow Caledonian University, UK. The substance could play a general role in protecting chemicals in the body from being broken down, he says.