Hurt Blocker
The next big pain drug may soothe sensory firestorms without side effects
Among a small number of related families from northern Pakistan, some individuals never feel pain in any part of their bodies. Scientists studying six such children found that by the age of 4, they all had injuries to the lips or tongue from repeatedly biting themselves. Bruises, cuts and broken bones were common, though fractures were diagnosed only long after the fact, when weird, painless limping or the inability to use a limb called attention to the injury. Tests showed that the pain-free children perceived sensations of warm and cold, tickling and pressure. They could feel the prick of a needle, but it didn’t hurt. Two had been scalded — painlessly — by hot liquids. And one boy who performed street theater by putting knives through his arms and walking on hot coals died after jumping off a roof on his 14th birthday.
Besides their inability to feel pain, the Pakistani individuals studied by the scientists had something else in common: mutations in a gene called SCN9A. That gene encodes the instructions for a protein that forms a passageway for letting sodium ions into nerve cells. Known as Nav1.7, this particular ion channel sits on pain-sensing nerves; when a nerve is stimulated enough to warrant sending a signal to the brain, a flood of sodium ions rush into the cell.