Can Marijuana Chemicals Make Good Medicine?

Nicholas Bakalar
for National Geographic News
October 13, 2005

Researchers are finding promising new evidence of the medicinal benefits of cannabinoids, the active ingredient in marijuana. But don't expect packages of pot to turn up on pharmacy shelves just yet.

Today a team of international researchers announced the discovery of CB2, the second cannabinoid receptor found in mammal brains.

Unlike the first receptor, discovered 15 years ago, CB2 activation reduces nausea without producing psychotropic side effects.

The new receptor is activated by endocannabinoids, which are cannabis-like chemicals produced in nerve cells and certain other cells in the body.

The team reports the findings in today's issue of the journal Science.

The Body's Own Cannabinoids

Cannabinoid receptors have been found in the brain, nervous system, spleen, thymus, and in various circulating immune cells.

Establishing the presence of the receptors in the brain involved a complex series of tests using ferrets. The researchers first found the gene for the receptor and looked to see whether the gene was "turned on" and creating the required proteins.

Molecular analysis demonstrated that the receptor was present on the ferrets' brainstem neurons. Other techniques allowed the researchers to see the consequences of activating the receptor, proving it works.

Keith A. Sharkey, the study's lead author, believes that the receptors will work the same way in humans as they do in ferrets.

He emphasizes, however, that this does not prove that smoking marijuana is a good treatment for nausea.

Drugs that originate outside the body, such as cannabinoids from smoked marijuana, "may not act at these receptors," said Sharkey, a professor of physiology and biophysics at the University of Calgary in Canada.

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