SAN DIEGO--Once considered a disease of old age, Parkinson's disease has been showing up in younger patients in recent years. Some researchers suspect that chronic drug abuse might spur a Parkinson's-like syndrome in some of these patients. Now, a team reported at the Society for Neuroscience meeting here that some young long-term cocaine addicts have abnormally high levels of a protein associated with Parkinson's in their brains.

Cocaine causes the signaling molecule dopamine to build up in the brain, resulting in continual stimulation of dopamine-sensing neurons. This dopamine overload can damage the cells that respond to the molecule--some of the same cells that wither in people with Parkinson's disease. Indeed, cocaine addicts going through withdrawal experience symptoms similar to Parkinson's disease, such as tremors.

To examine what long-term cocaine addiction does to the brain, researchers led by neuroscientist Deborah Mash at the University of Miami took advantage of Dade County, Florida's, dismal death toll. The county, in which Miami is located, has one of the nation's highest cocaine-related death rates. Looking at brain tissue from cocaine addicts who died suddenly, Mash's team stained the samples with an antibody against a protein called a -synuclein. Clumps of this protein are a hallmark of Parkinson's disease, although researchers aren't sure what causes the buildup. Compared with drug-free individuals of the same average age--early 30s--the addicts had 3 times as much a -synuclein, while levels of a related protein, b -synuclein, were normal.

The findings are "highly provocative," says neuroscientist Steven Grant of the National Institute on Drug Abuse in Bethesda, Maryland. "I wouldn't have expected this." But he cautions that the results will have to be replicated to confirm that cocaine use is linked to the buildup of this toxic protein.

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Abstract from Society for Neuroscience meeting