Brain Chemicals Suggest Marijuana's Effects

Natural Substances May Mirror Pot's Effects on the Brain

From the WebMD Archives

Sept. 15, 2004 -- Marijuana is well known for its widespread effects on the brain. The key to understanding its impact may come from the brain's own pharmacy.

Brains make their own calming substances called cannabinoids, which are similar to marijuana's active ingredients.

Cannabinoids are made in the brain's cortex, an area which processes sensory information and orchestrates movement, thinking, learning, and emotions.

Scientists already knew that the cells in this area of the brain can make their own cannabinoids.

These cells (pyramidal) normally work to excite neighboring cells; using their homemade cannabinoids temporarily allows more information to be processed by lowering the brain's inhibition of excess information processing. By lulling other brain cells, cannabinoids temporarily leave the pyramid cells free to fire away.

Now, researchers at Stanford University in California have found that other type of brain cells -- LTS cells -- can also make cannabinoids.

LTS cells ordinarily keep pyramid cells in check. This process works to guard too much information being processed from pyramidal cells to neighboring cells within the brain region.

But when LTS cells make their own cannabinoids, they tune themselves out from surrounding cells.

As a result, the brain's pyramid cells are temporarily freed from inhibition. They then process excess information to other cells.

The effects can last up to 35 minutes.

Marijuana's active ingredients may behave the same way, latching on to these cannabinoid receptor sites allowing information to be process in an altered way.

"A loss of inhibition in pyramid cells could produce changes in perception, in motor function, and in everything the cerebral cortex does," researcher David Prince, MD, says in a news release.

Studying cannabinoid receptors may one day lead to drugs for conditions such as epilepsy, says Prince, the Edward F. and Irene Thiele Pimley professor of neurology and neurosciences at Stanford University School of Medicine.

During seizures pyramidal cells fire out of control, one reason may be that neighboring cells get shut down. Targeting and blocking cannabinoid receptors might quiet pyramidal cells activity.

Prince and Stanford colleagues based their study on lab rats. Their report appears in the Sept. 16 issue of Nature.

SOURCES: Prince, D. Nature, Sept. 16, 2004. News release, Stanford University Medical Center.