Congenital insensitivity to pain is a rare condition, affecting about one in one million. There are various gene mutations that can cause the condition.
One way is the vertical transfer of mutated SCN9A genes from parents to offspring. The condition requires two copies of the mutated SCN9A gene, each copy contributed by a parent that typically showed no signs of carrying one.
Those mutations, in SCN9A and other genes, impact Nav1.7 channels, which carry sodium along nerves between pain sites and the brain.
Previously, researchers looked for ways to treat the mutated genes. Just this summer researchers reported progress in treating the PRDM12 gene, hoping to use it as a lever to turn other genes on or off.
But lately, a team from University College London went back to studying Nav1.7 channels. And they found that poorly operating Nav1.7 channels also encouraged production from the genes responsible for the release of opioids peptides, dulling the sensation of pain with the body's natural pain killers.
The research team then flipped the puzzle around by looking to inhibit opioid receptors, which gobble up opioids brewed in a brain and introduced through a syringe all the same. Naloxone is used to shut off the receptors in the event of an opioid overdose, so the team decided to use with a different objective in mind.
And finding success with lab mice, the researchers administered naloxone to a 39-year-old woman who had never been able to feel pain. After the naloxone, she could feel the burn of a laser.
While people with congenital insensitivity to pain may be encouraged by the study, the long-term use of naloxone would likely do more harm than good. But for people who wish they didn't feel nearly as much pain as they do, the study may bear fruit for them in the near future.
When combined with Nav1.7 blockers, a "very low" dose of an opioid could be an effective way to treat pain and help people avoid falling into opioid addition, stated John Wood, senior author and professor at University College London.
"People with non-functioning Nav1.7 produce low levels of opioids throughout their lives without developing tolerance or experiencing unpleasant side-effects," Wood said. "We hope to see our approach tested in human trials by 2017 and we can then start looking into drug combinations to help the millions of chronic pain patients around the world."
The study was published in the journal Nature Communications on Dec. 4, 2015.