STUDY: MARIJUANA, MORPHINE WORK ON SAME AREA OF BRAIN

WALNUT CREEK, Calif. - A new study shows that the active ingredient in
marijuana combats pain in the same part of the brain as morphine,
potentially giving pot-for-pain advocates more fuel to make the prohibited
drug available for suffering patients.

Researchers at the University of California at San Francisco have shown for
the first time that delta-9-THC, the active ingredient in marijuana, stops
pain signals in the base of the brain before they reach pain-awareness
centers.

Doctors and patients have claimed for years that smoking marijuana helps
their patients cope with immense pain caused by injuries or chronic
diseases such as AIDS or cancer, based mostly on anecdotal evidence and
studies conducted in the early 1970s.

In 1996, California voters agreed and passed Proposition 215, which allows
marijuana for medical uses. But scientific evidence has been lacking and,
despite Prop. 215, federal law-enforcement agencies have shut down attempts
to distribute the drug.

The UC-San Francisco study and additional medical studies may be key to
persuading federal agencies to let doctors use the drug, said Steve Heilig,
director of the San Francisco Medical Society - the only medical
organization to endorse Prop. 215 during the campaign.

The UC-San Francisco animal study shows that THC affects the same part of
the brain as morphine, a common treatment for severe pain.

"There is absolutely no question that it has an impact," said Ian Meng, a
post-doctoral researcher and primary author of the study, published today
in the scientific journal Nature. "It was really clear."

Research on humans has been unable to dissociate the drug's pain-numbing
positives with its mind-altering side effects because they couldn't go into
the brain and find out where the drug was working, Meng said. In recent
years, several studies have shown that THC is effective in treating
localized pain, such as that around wounds, and in stopping pain at the
spinal cord. But none has shown if it worked in the brain to stop pain.

Meng and other UC-San Francisco researchers injected rats with a synthetic
form of the drug and tested the animals' response to pain. They compared
the rats' reaction to THC with their reaction to morphine and found that
both drugs work at the base of the brain near the spinal cord, turning off
some pain messages and preventing others from being amplified as they
travel to the brain regions that regulate how pain is perceived.

"It is an important finding," said Michael Walker, a Brown University
professor of psychology and neuroscience who has studied THC's impact on
pain messages traveling through the spinal cord. "We previously showed that
cannabinoids (marijuanalike drugs) suppress the response of stimuli, but we
don't know much about how they do that."

Although THC works on the same part of the brain as morphine, researchers
found it does not work in the exact same way. That means further studies
should examine whether the drugs could be used together to treat pain, Meng
said. Other potential research areas include finding out exactly how THC
works in the brain stem and exploring better ways to deliver the dose, such
as by pill or inhaler, because smoking it damages the lungs.