Nicotine protects brain cells most affected by Parkinson's disease, studies in monkeys show.
The findings, by Maryka Quik, PhD, and colleagues at The Parkinson's Institute in California, indicate nicotine might slow Parkinson's if given very early in the disease process.
They also help explain why cigarette smokers get Parkinson's disease less often than nonsmokers.
Parkinson's disease occurs when brain cells that produce dopamine — an important chemical messenger — die off.
Nicotine may protect these cells from toxic damage.
In their study, Quik and colleagues spiked squirrel monkeys' drinking water with nicotine so the animals' blood levels of the drug were similar to that in human smokers.
After six months on nicotine, the researchers gave the monkeys a toxin that kills the dopamine-producing cells and mimics the effects of Parkinson’s.
The toxin did 25 percent less cell damage to the brains of the nicotine-treated monkeys.
Quik and colleagues note that people don't get Parkinson's symptoms until 80 percent to 90 percent of their dopamine-producing cells are dead.
"This means that a reduction in [brain cell] damage from 80 percent to 60 percent can mean the difference between having disease symptoms and being symptom-free," Quik says, in a news release.
People worried about Parkinson's disease should not all start smoking, warns David A. Schwartz, MD, director of the National Institute of Environmental Health Sciences, the agency that funded the Quik study.
"While we would never recommend that people smoke, these results suggest that nicotine promotes the survival of dopamine-producing cells in animals with no overt Parkinson's symptoms," Schwartz says, in a news release. "These findings have implications for its use in slowing the progression of Parkinson's."
It's not clear how nicotine protects these crucial brain cells. Quik and colleagues suggest the drug may stimulate release of brain chemicals that help nerve cells grow and recover from injury.
The study appears in the early online edition of the Journal of Neurochemistry.
By Daniel J. DeNoon, reviewed by Louise Chang, MD
SOURCES: Quik, M. Journal of Neurochemistry, 2006; early online edition. News release, The Parkinson's Institute.