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Why Marijuana May Affect Memory

Study in Rats Shows Pot-Like Substance Disrupts Brain Cell Coordination
WebMD Health News
Reviewed by Louise Chang, MD

Nov. 20, 2006 -- A new study on marijuana and memory may show why using pot hampers memory.

The study appears in Nature Neuroscience's advance online edition.

Researchers included David Robbe, PhD, of the Center for Molecular and Behavioral Neuroscience at Rutgers, the State University of New Jersey.

The study was in rats, not people.

The researchers gave rats shots of a synthetic cannabinoid drug that resembles marijuana's active ingredient, THC (tetrahydrocannabinol).

The drug doses were "comparable with recreational and palliative [pain relief] uses in humans," note Robbe and his colleagues.

For comparison, other rats got saltwater shots without cannabinoids.

Twenty minutes later, the scientists started monitoring the activity of certain nerve cells, or neurons, in the rats' brains.

Those neurons normally send chemical signals to communicate with each other. The process occurs seamlessly, like musicians playing in sync with each other in an orchestra.

But after the cannibinoid shots, the rats' neurons lost their coordination.

The neurons sent their chemical signals at the usual rate, but they were out of step with each other, like an orchestra in which musicians play without working together.

The problem was not seen with the saltwater shots.

The findings may explain how marijuana impairs memory, Robbe's team notes. However, the scientists didn't test the rats' memory.

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