DURHAM, N.C. -- Neuroscientists at Duke University Medical Center working with genetically engineered mice have found that the brain chemical dopamine plays a critical role in regulating sleep and brain activity associated with dreaming.
When dopamine levels were dramatically reduced, the mice could no longer sleep, the scientists said. When dopamine levels were increased, the mice exhibited brain activity associated with dreaming during wakefulness.
The same processes likely occur in humans, according to the researchers. They said the findings give insight into the sleep problems common among patients suffering from Parkinson's disease, a neurodegenerative disorder in which brain cells containing dopamine die or become impaired.
"Our study may lead to development of new diagnostic tools for the early detection of Parkinson's disease based on the sleep disturbances that are often associated with motor symptoms of the disease," said senior study investigator Miguel Nicolelis, M.D., Ph.D., Anne W. Deane professor of neuroscience.
The findings may also provide a mechanism to explain some of the symptoms, such as hallucinations, experienced by psychotic and schizophrenic patients, he said.
The researchers published their findings in the Oct. 11, 2006, issue of the Journal of Neuroscience. The work was supported by the National Institutes of Health, the Hereditary Disease Foundation and the Anne W. Deane professorship to Nicolelis.
Parkinson's disease occurs when the brain cells, or neurons, that normally produce dopamine die or become impaired. Once 60 percent to 70 percent of the neurons are knocked out of commission, the jerky movements and fixed facial expressions characteristic of Parkinson's appear.
The new study suggests that destruction of significantly fewer dopamine-producing cells could result in sleep problems long before the motor problems become apparent, the researchers said.
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