39-year-old feels pain for the first time, say scientists

LONDON: A 39-year-old woman has felt pain for the first time in her life, following an experiment that could lead to new ways of treating people with chronic conditions, scientists say.

The woman, who wished to remain anonymous, was born with a condition that prevented her from feeling any pain, but a drug normally used to treat drug addiction made her sensitive to a hot laser beam.

Scientists said that the woman “quite enjoyed” the mildly painful sensation of being heated by the laser, which was a novel experience for someone who has been unable to feel any pain since she was a baby. A handful of people each year are born with a genetic mutation that blocks an “ion channel” in the pain-sensing nerves. Babies born with blocked pain channels need special care because they tend to chew their fingers, lips and toes until they bleed, and toddlers are at increased risk from damaging themselves by knocks and tumbles or contact with hot or sharp objects.

The woman was known to have inherited a mutation in a gene that blocked an ion channel called Nav1.7, which carries sodium ions across the nerve membrane and allows the transmission of pain signals to the brain.

Laboratory mice that were genetically modified to lack the Nav1.7 gene also show an inability to feel pain. This has allowed scientists to develop an animal model of the human condition - and in the process discover a new way of treating chronic pain.

A number of drugs have been developed to block the Nav1.7 nerve channels in the hope they would be promising pain killers, but produced disappointing effects. Scientists say they have found a way around the problem.

John Wood of University College London has shown that both mice and people with the genetic mutation produce higherthan-normal levels of the body’s natural painkillers, the opioid peptides of the brain. To examine whether this was important for losing the sense of pain, the researchers administered a drug called naxalone, which is used to treat heroin addiction, and found that both the mice and the woman were suddenly able to feel pain again. “After a decade of rather disappointing drug trials, we now have confirmation that Nav1.7 really is a key element in human pain,” said Professor Wood, the senior author of the study. – The Independent