How to Stick a Knife Through Your Arm
I know that probably sounds a bit gross, but sometimes Nature does our experiments for us.
And this particular experiment involved a young Pakistani boy who worked as a street "entertainer" by sticking sharp objects into various parts of his anatomy. He was able to do this not because of some form of religious fervor or yogic control, but because he had a congenital inability to feel pain.
That may sound like a good thing but it is not. Pain exists to warn you: how else would you know is you have stepped on broken glass or put your hand on a hot plate?
Investigators on three continents collaborated to track down the boy’s problem at the molecular level. The research is published in the journal Nature, and will likely open up a whole new approach to treating pain.
The boy dies four years ago at the age of fourteen, but the investigators were able to track down six of the boy’s extended relatives who were also totally numb to pain. However they had some feeling: a pinprick would feel like pressure. They all had frequent cuts and bruises and problems using their limbs, and they all had old injuries to their lips or tongues from biting themselves as young children.
Since the late 1990s researchers have been studying the culprit gene product, a sodium-conducting ion channel called NaV1.7, which sits on the ends of pain-sensing cells. In 2004 researchers in China identified members of two families who have a nasty condition called erythromelalgia, in which the slightest warmth causes literally burning pain in their hands and feet.
Work by the group in China and Stephen Waxman’s group at Yale in West Haven, Connecticut, discovered that the cause of this condition is a mutation in the NaV1.7 channel that makes it become hyperactive. In effect the mutated channel overstimulates pain-sensing neurons, causing them to register pain more frequently. By contrast, the mutation in the pain-free Pakistanis knocks out NaV1.7 activity, so no firing of the pain-sensing neurons.
This work will inevitably lead to a search for new ways of damping down pain. Now that we have a good idea of the way in which a single mutation can either cause too much pain or none at all, the nest step is to see if we can deelop comprehensive treatment strategies based on these new insights.