Solving the secret of why a rare genetic mutation stops some people feeling any pain may lead to new therapies to help those who suffering from it chronically, a study has found.
The study carried out by University College London (UCL), and published in Nature Communications, found a particular "channel" used by the body for electrical signals was the key to people's painlessness.
The research saw a woman (39), who was born with pain free condition, being tested by scientists and experiencing pain for the first time in her life.
UCL Prof John Wood, a senior author of the report, said only about 30 people in the world had the rare painlessness genetic condition.
“These people are normal, they don’t have any side effects and are completely functional,” he said.
They still felt touch that was not painful normally and the only known side-effect was the inability to smell, he said.
Prof Wood said the woman was given naloxone, an opioid peptides blocker, to reverse the disorder.
"We hit her with a laser in the arm and she could never feel it. Then she said it hurt, and she had never felt pain before," Prof Wood told The Irish Times.
“She said ‘I’m so pleased about this. If I’ve any children with the same condition they won’t have to go around damaging themselves’. Pain is a fantastic protective system.”
Opioid painkillers such as morphine are highly effective at reducing pain. However long-term use can lead to dependence and tolerance. He said testing on genetically modified mice was essential to find that a lack of the channel, called nav1.7, showed a higher production of natural opioid pain relievers.
“Studying the mice showed us what was going on in the nervous system that led to painlessness and our findings were directly translatable to humans, as confirmed by the painless patient,” he said.
Prof Wood said it looked like researchers could “mimic” the pain free condition with drugs.
“After a decade of rather disappointing drug trials, we now have confirmation that nav1.7 really is a key element in human pain,” he said.
“It suggests a new therapy for pain. Pain affects about 20 per cent of the population. There are millions of people that are not adequately treated.”
Prof Wood said he hoped to see the approach in human trials by 2017 and then research drug combinations to help chronic pain patients.
“We’re confident that we can but you can never be sure,” he said. “People with non-functioning nav1.7 produce low levels of opioids throughout their lives without developing tolerance or experiencing unpleasant side-effects.
“The secret ingredient turned out to be good old-fashioned opioid peptides, and we have now filed a patent for combining low dose opioids with nav1.7 blockers.”
The study was funded by the MRC and Wellcome Trust.
