Researchers Target New Ways to Stop Chronic Pain

From the WebMD Archives

Feb. 20, 2000 (Washington) -- Bump your head or prick your finger, and you might feel a twinge of pain. But for some people, such as those with back injuries, pain is a constant part of life. This chronic pain can be devastating to its victims, but researchers at a conference here Sunday have been working to better understand such pain in order to find better ways to treat it.

One of those researchers, Catherine Bushnell, PhD, a professor at McGill University in Montreal, and her colleagues used magnetic resonance imaging (MRI) to understand which human brain circuits become active when a person feels a hot object or hears a painfully loud sound. The experiments identified two brain areas. "No matter how the pain is produced, there is a common circuit that tells us it is pain," she says.

Bushnell and her team next tested the effect of hypnosis on pain perception. The researchers placed people involved in the study under hypnosis and suggested that they would no longer experience a painful sensation as unpleasant. When the individuals were tested a week later, they felt less pain, suggesting that hypnosis might be a useful treatment.

"It's important for [patients and physicians] to understand that they do have some control over their pain," she says.

But Bushnell and other researchers emphasized that it is important not to blame the victim. That's because chronic pain, unlike the acute pain we feel after bumping our head, is a real and debilitating condition.

"Persistent pain is not just a symptom," says Allan Basbaum, PhD, professor of anatomy at the University of California at San Francisco. "It is a disease, and it needs to be treated as a disease." Basbaum and Bushnell were both speaking at the annual meeting of the American Society for the Advancement of Science.

Another researcher at the conference, Jeffrey Mogil, PhD, has been working to try to figure out why an injury that might feel mild to some people can feel agonizing to others. His research is revealing that there may be genetic differences in pain perception between different individuals, and between men and women. The research, which is currently being conducted in mice, could one day lead to pain medication tailored to individuals.

Until recent years, no one had much of an idea which molecules in the cell were responsible for perceiving pain. But recent progress in the field has begun to uncover proteins in cells that seem to work specifically to determine how pain is sensed, says Basbaum.

To identify the genes responsible for these proteins, Mogil and his colleagues examined how various inbred strains of mice perceive pain. All individuals of an inbred strain of mice are genetically identical, but each strain differs genetically. Mogil is a professor of psychology at the University of Illinois at Urbana-Champaign.

Mogil's team tested the pain threshold of different mice by placing their paws on a hot plate that was warm enough to hurt but not hot enough to burn. Then, the researchers measured how long it took for the mice to lift their paw and shake it. The mice feel pain only temporarily, says Mogil.

The Illinois team identified differences in pain threshold between male and female mice, as well as differences between individuals of the same sex.

The researchers are now collaborating with other researchers to search among these genes for the ones that control an individual mouse's pain threshold. When the genes can be identified, they may offer molecular targets for gene therapy to treat chronic pain, he says.