New Way to Treat Chronic Pain Shows Promise

In a series of animal studies, scientists have demonstrated the therapeutic potential of selectively deleting specific nerve cells from the nervous system that convey severe chronic pain. Their findings were published in the May 1, 2004, issue of the Journal of Clinical Investigation.

The treatment was used on eight dogs severely affected by osteroarthritis, cancer, or both. All eventually became more active and later walked with slight or no limps. None showed any adverse side effects from the treatment and their need for other pain-controlling medications was eliminated or greatly reduced. The researchers also selectively deleted the nerve cells called C-fiber neurons from various human neurons cultured together in the laboratory, an indication that the strategy might work in people. C-fibers convey sensations of noxious heat and certain inflammatory signals to the central nervous system.

The treatment is based on using an old drug called resiniferatoxin (RTX) a new way. RTX attaches to a protein called vanilloid receptor 1(VR1), displayed on the surface of certain types of heat-pain-sensing neurons, and prompts a brief influx of calcium through a channel but only in those cells that manufacture the ion channel. This RTX-induced flow of calcium can overdose, seriously disable, and ultimately kill these neurons. By applying RTX directly to the dorsal root ganglia, the scientists knew they could selectively delete specific neurons, such as C-fibers, that exhibit large amounts of VR1 protein. This led to the idea of permanently turning off their chronic pain signals.

"We realized that by focusing on RTX's ability to kill cells, we could apply it therapeutically,” said lead author Dr. Laszlo Karai, a scientist at the U.S. National Institute of Dental and Craniofacial Research (NIDCR, Bethesda, MD, USA). "The technique selectively deletes certain neurons but leaves other untouched.”





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National Institute of Dental and Craniofacial Research