Posts tagged congenital analgesia
Articles and news from the latest research reports.
Girl who feels no pain could inspire new painkillers
A girl who does not feel physical pain has helped researchers identify a gene mutation that disrupts pain perception. The discovery may spur the development of new painkillers that will block pain signals in the same way.
People with congenital analgesia cannot feel physical pain and often injure themselves as a result – they might badly scald their skin, for example, through being unaware that they are touching something hot.
By comparing the gene sequence of a girl with the disorder against those of her parents, who do not, Ingo Kurth at Jena University Hospital in Germany and his colleagues identified a mutation in a gene called SCN11A.
This gene controls the development of channels on pain-sensing neurons. Sodium ions travel through these channels, creating electrical nerve impulses that are sent to the brain, which registers pain.
Blocked signals
Overactivity in the mutated version of SCN11A prevents the build-up of the charge that the neurons need to transmit an electrical impulse, numbing the body to pain. “The outcome is blocked transmission of pain signals,” says Kurth.
To confirm their findings, the team inserted a mutated version of SCN11A into mice and tested their ability to perceive pain. They found that 11 per cent of the mice with the modified gene developed injuries similar to those seen in people with congenital analgesia, such as bone fractures and skin wounds. They also tested a control group of mice with the normal SCN11A gene, none of which developed such injuries.
The altered mice also took 2.5 times longer on average than the control group to react to the “tail flick” pain test, which measures how long it takes for mice to flick their tails when exposed to a hot light beam. “What became clear from our experiments is that although there are similarities between mice and men with the mutation, the degree of pain insensitivity is more prominent in humans,” says Kurth.
The team has now begun the search for drugs that block the SCN11A channel. “It would require drugs that selectively block this but not other sodium channels, which is far from simple,” says Kurth.
Completely unexpected
"This is a cracking paper, and great science," says Geoffrey Woods of the University of Cambridge, whose team discovered in 2006 that mutations in another, closely related ion channel gene can cause insensitivity to pain. "It’s completely unexpected and not what people had been looking for," he says.
Woods says that there are three ion channels, called SCN9A, 10A and 11A, on pain-sensing neurons. People experience no pain when either of the first two don’t work, and agonising pain when they’re overactive. “With this new gene, it’s the opposite: when it’s overactive, they feel no pain. So maybe it’s some kind of gatekeeper that stops neurons from firing too often, but cancels pain signals completely when it’s overactive,” he says. “If you could get a drug that made SCN11A overactive, it should be a fantastic analgesic.”
"It’s fascinating that SCN11A appears to work the other way, and that could really advance our knowledge of the role of sodium channels in pain perception, which is a very hot topic,” says Jeffrey Mogil at McGill University in Canada, who was not involved in the new study.
(Source: newscientist.com)
The Hazards of Growing Up Painlessly
The girl who feels no pain was in the kitchen, stirring ramen noodles, when the spoon slipped from her hand and dropped into the pot of boiling water. It was a school night; the TV was on in the living room, and her mother was folding clothes on the couch. Without thinking, Ashlyn Blocker reached her right hand in to retrieve the spoon, then took her hand out of the water and stood looking at it under the oven light. She walked a few steps to the sink and ran cold water over all her faded white scars, then called to her mother, “I just put my fingers in!” Her mother, Tara Blocker, dropped the clothes and rushed to her daughter’s side. “Oh, my lord!” she said — after 13 years, that same old fear — and then she got some ice and gently pressed it against her daughter’s hand, relieved that the burn wasn’t worse.
“I showed her how to get another utensil and fish the spoon out,” Tara said with a weary laugh when she recounted the story to me two months later. “Another thing,” she said, “she’s starting to use flat irons for her hair, and those things get superhot.”
Tara was sitting on the couch in a T-shirt printed with the words “Camp Painless But Hopeful.” Ashlyn was curled on the living-room carpet crocheting a purse from one of the skeins of yarn she keeps piled in her room. Her 10-year-old sister, Tristen, was in the leather recliner, asleep on top of their father, John Blocker, who stretched out there after work and was slowly falling asleep, too. The house smelled of the homemade macaroni and cheese they were going to have for dinner. A South Georgia rainstorm drummed the gutters, and lightning illuminated the batting cage and the pool in the backyard.
Without lifting her eyes from the crochet hooks in her hands, Ashlyn spoke up to add one detail to her mother’s story. “I was just thinking, What did I just do?” she said.