No Pain Is Science's Gain
By Malin Sandström
ScienceNOW Daily News
13 December 2006

Pain is hard to live with but near impossible to survive without. Now, thanks to a handful of children who cannot feel pain, researchers have identified a key protein responsible for pain sensation. The finding, say experts, could lead to new and better medications for treating both chronic and temporary pain.
The genetic basis of pain has remained elusive until the last few years. Several recent investigations of families with inherited pain disorders have flagged a kind of sodium channel, called Nav1.7, which is plentiful in sensory neurons. Overactive Nav1.7 channels can cause recurring throbbing or sudden paroxysms of pain. Yet it has been unclear whether Nav1.7 is the root of the pain, or if the pain is caused by defects in the channel's activity.

Six children who are immune to pain may have finally provided the answer. Unlike other people with pain insensitivity, the children have no other neural problems: They have normal perception of cold and warmth; they can feel touch and pressure; and they have normal reflexes. "The neurons seem to be there, and they seem to be normal. But they seem not to pick up the [pain] signal," says clinical biochemist Frank Reimann of the Cambridge Institute for Medical Research in the United Kingdom, part of a team that studied the children.

All six children, from three related families, have mutations in a gene called SCN9A, which codes for a subunit of the Nav1.7 sodium channel. A genetic analysis by the team has now revealed that the mutations take the Nav1.7 channel out of action. That means Nav1.7 is a critical player in the body's ability to sense pain, the team reports tomorrow in Nature.

Pediatrician Mark Gardiner of University College of London agrees. "This channel has an absolutely key role in the transmission of pain sensation," says Gardiner, who performs related research on inherited pain disorders. "It all fits together quite nicely." Because the children with the SCN9A mutation are otherwise normal and healthy, it could be possible to block the Nav1.7 sodium channel in those with pain disorders without any apparent side effects, he says. "If you could block this channel, you could potentially have a very powerful analgesic."