BROWN U. STUDY: BRAIN RESPONDS TO PAIN WITH MARIJUANA-LIKE SUBSTANCE

Brown researchers have discovered that a person's brain modulates pain by
releasing a cannabinoid similar to delta-9-THC, the active ingredient in
marijuana. In the words of researcher and graduate student Susan M. Huang,
"the brain makes its own marijuana."

Professor of Psychology J. Michael Walker led the study, the findings of
which were published in the Oct. 12 issue of the Proceedings of the
National Academy of Sciences. The cannabinoid, called anandamide, dulls
pain in a person's body. When a person is cut, for example, their body
releases more anandamide to help deal with the extra pain.

This discovery could explain why different people have different pain
thresholds, Huang said. Depending on how much anandamide a person's body
releases, they may experience pain in different degrees. However, much more
research is needed to verify these hypotheses.

As for the effects of this discovery on the marijuana-legalization debate,
policy-makers could easily ignore the study, like many similar reports
before it, Walker said.

"I work in the scientific community," Walker said, "and I've noticed that
there's a political theater that invokes science only occasionally."

Walker said that the study's recommendations for marijuana use are worth
looking at, but he also said that "you don't want people to injure their
foot and say 'I'm going to go smoke some weed.' That's not the first step.
... Go take some Advil."

Researchers discovered the function of anandamide with the help of a new
technique called microdialysis. They collected and measured anandamide that
had dissociated from the nerve cell receptors in brains of anesthetized rats.

Anandamide is produced in a region of the brain called the periaqueductal
gray (PAG). Using a mass spectrometer, researchers were able to detect tiny
amounts of anandamide floating in the PAG's extracellular space.

Walker is grateful to Brown for buying the spectrometer, a tool that he
said "cost more than my first house."

The research team did most of the work on this project in the last six or
seven months, although Walker said he has been working on it for about 10
years. Prior to their use of the mass spectrometer, researchers knew that
the brain's cannabinoids caused changes in behavior but weren't aware of
the cannabinoids' effect on pain modulation.

The next step, according to Huang, is to find out more about the pathways
connecting the brain's release of anandamide and the area of the body
experiencing pain. "We hope to look more into the mechanisms that mediate
this response," Huang said.

Besides Walker and Huang, researchers included M. Clara Saudo-Pea,
assistant research professor of psychology, and Nicole M. Strangman GS.

The project was financed by the U.S. Public Health Service and National
Institutes of Health. The National Institute on Drug Abuse also helped the
University buy the mass spectrometer.