"This model is exciting because it allows us to examine the potential contribution of systems other than dopamine to Parkinson's disease," said Caron. "We may be able to discover avenues for treatment that had never been thought about before or that were impossible to investigate."

The new mouse model enables the researchers to acutely eliminate dopamine, exposing systems contributing to the disease that may not have been obvious before, he explained. The severity of disease symptoms in the mice also provides a very sensitive test for compounds with potential therapeutic value, the researchers said.

In the United States, at least 500,000 people suffer from Parkinson's disease, and about 50,000 new cases are reported annually, according to the National Institute of Neurological Disorders and Stroke. These figures are expected to rise as the average age of the population increases. Symptoms of the disease include tremors, slow movement or an inability to move, rigid limbs and a shuffling gait. Progression of the disease also leads to severe impairment in cognitive function.

Dopamine replacement therapy which involves administration of the dopamine precursor, L-DOPA, remains the gold standard for Parkinson's treatment, said Tatyana Sotnikova, Ph.D., of Duke. However, the efficacy of the therapy wanes with time, and patients often develop fluctuations in motor performance and other adverse reactions.

In the current study, the researchers treated mice unable to recycle dopamine with a drug that also prevented them from manufacturing the brain messenger. The brains of the mice therefore lack detectable levels of dopamine and the animals exhibit all the symptoms of Parkinson's disease for up to 16 hours. Those symptom
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Contact: Kendall Morgan
kendall.morgan@duke.edu
919-684-4148
Duke University Medical Center
1-Aug-2005