Source: San Francisco Examiner (CA) Contact: Website: Pubdate: September 23, 1998 Author: Ulysses Torassa, Examiner Medical Writer


Research adds to evidence drug is medically useful

A circuit in the brain stem that is switched on and off by the active ingredient in marijuana is the latest in a mounting pile of scientific evidence pointing to the drug's ability to kill pain, a new UC-San Francisco study said Wednesday.

The substance, a synthetic form of THC (tetrahydrocannabinol), has an effect similar to morphine in an area at the base of the skull that is known to block pain impulses.

Importantly, researchers found that the substance uses a different way to trigger the blockage, suggesting that marijuana-like drugs might be developed as effective painkillers without the unwanted side effects of opiates.

The area of the brain where the substance is active is known to block pain messages in extremely stressful situations like war, in which people have reported not feeling pain despite catastrophic injuries.

The study, to be published in Thursday's issue of the journal Nature, comes in the midst of continuing debate over the therapeutic use of marijuana.

Five states and the District of Columbia have initiatives on the November ballot similar to California's Proposition 215, which allows seriously ill patients to grow and use marijuana for pain relief, with a doctor's recommendation, without being prosecuted under state law.

To cannabis advocates like Chuck Thomas of the Marijuana Policy Project, the study is further proof that the thousands of people with cancer, AIDS and other diseases who are using the drug to feel better are on the right track.

"These patients are not stupid and should not be going to jail," Thomas said.

The drug is also receiving more attention from scientists. The UCSF study is one of several that have demonstrated painkilling properties of cannabinoids, the substances that are the major active ingredient in marijuana.

"A hot field'

"It's definitely a hot field right now," said UCSF's Ian Meng, author of the study reported in Nature. "There is a breakthrough every month, it seems. Scientists have really been taking a serious look at what cannabis can do."

In Meng's experiments, a synthetic cannabinoid was given to two sets of laboratory rats - one in which the region of the brain stem involved in pain blockage was normal, and one group in which it was deactivated.

The rats with the deactivated region showed no difference in their response to pain from rats without the drug. But those who had normal brain stems took longer to respond to a painful stimulus after receiving the cannabinoid.

The results show that the cannabinoids are working directly at that site, which is also where morphine works. The experiments also worked when Meng gave the rats a drug that blocks the action of morphine, indicating the pathways used by the two drugs are different.

"I think in the future you'll see different kinds of drug combination therapies, where you can use cannabis-like drugs with a lower dose of a morphine compound and possibly reduce side effects," Meng said.

Morphine, which is highly addictive, can be fatal in high doses by depressing a patient's breathing and inducing nausea. Cannabis, on the other hand, has been shown to stimulate appetite and is much less addictive.

UC-Irvine study

Scientists at UC-Irvine reported this summer that cannabinoids cut down on pain when applied directly at the site of a wound. University of Texas researchers have also found the chemicals relieve arthritis-like inflammation, and scientists at the University of Minnesota recently showed the chemicals can be used to block a form of extreme sensitivity to pain called hyperalgesia.

The National Academy of Sciences is also expected to report late this year on scientific evidence for the use of marijuana in medical treatments and recommendations for policy.

"It's time for society and public policy to really look at the science that's out there," Meng said.

J. Michael Walker, a neuroscientist at Brown University, also observed in 1995 and 1996 the painkilling effects of cannabinoids in the brain stem. He said the field has taken off since 1990, when scientists finally learned that many brain cells in areas that control pain contain receptors for cannabinoids.

"There's a lot of this receptor in the brain, it's loaded up with this stuff," Walker said. "It's very exciting, from the neurobiology point of view."

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