Fiery plant sap helps canine lick cancer pain

Lauran Neergaard Associated Press Jan. 17, 2006 12:00 AM

WASHINGTON - The dog hopped on three legs, with pain from bone cancer so bad that he wouldn't let his afflicted fourth paw touch the floor. His owner was bracing for euthanasia when scientists offered a novel experiment: They injected a fiery sap from a Moroccan plant into Scooter's spinal column, and the dog frolicked on all fours again for several months.

The chemical destroyed nerve cells that sensed pain from Scooter's cancer, not helping the tumor but apparently making him no longer feel it.

The dramatic effect in dogs has researchers from the National Institutes of Health preparing to test the chemical in people whose pain from advanced cancer is unrelieved by even the strongest narcotics.

The first human study could begin by next year at the NIH's Bethesda, Md., hospital. A second study in pain-ridden dogs is slated for this summer at the University of Pennsylvania.

If the research pans out, it might one day offer doctors and veterinarians a desperately needed new approach to attack intractable pain. And it's from an unlikely source, a cousin of the chemical that makes chile peppers hot.

Why would a substance that feels like it's burning a hole in your tongue - yes, one researcher tasted it - relieve pain, too?

This chemical, called resiniferatoxin or RTX, can poison nerve cells that control a type of heat-related inflammatory pain, apparently eliminating one of the body's pain-sensing systems. Yet it doesn't seem to harm other nerves that sense, say, the sharp pain from stepping on a tack.