A Surprising Player in Parkinson’s Disease
News from the Frontier

by Elizabeth Norton Lasley

March, 2007

The symptoms of Parkinson’s disease, ranging from tremors to complete loss of movement, result from a shortage of dopamine in a brain area known as the striatum. But dopamine may not work alone: endocannabinoids, the brain’s naturally occurring compounds similar to those found in marijuana, may also play a role in regulating movement.

Using a new approach that boosts levels of both chemicals at once, researchers at Stanford University Medical School restored normal movement to mice with a condition similar to Parkinson’s disease.

Brain cells reconfigure their connections in a process known as plasticity, which, in the striatum, is dopamine-dependent. Reporting online in the February 7 Nature, Robert Malenka [a BrainWork advisor] and Anatol Kreitzer found that certain striatal neurons are the only ones to undergo a specific type of plasticity, which requires the action not only of dopamine but also of endocannabinoids.

To test the effectiveness of targeting both brain messengers, the researchers treated mice that had a Parkinson’s-like condition with a dopamine-enhancing medication plus a chemical that prevents the breakdown of endocannabinoids. The two-pronged approach yielded striking results: Mice that were almost frozen in place began moving freely in as little as 15 minutes.

The interactions these drugs target may open new avenues for treatment, but Malenka cautions that smoking marijuana will not cure Parkinson’s disease. “Our procedure boosted a release of the brain’s own compounds in specific cells,” which smoking marijuana would not do, he notes.