In about 10 percent of patients, Parkinson's strikes before age 50. These rare cases probably are caused by inherited genetic abnormalities. However, most patients show their first Parkinson's symptoms after age 60. Researchers believe older patients may have suffered brain damage from chronic exposure to unspecified toxins. In the experiment conducted at Emory University in Atlanta, neurologists implanted tiny pumps in the rats to continuously administer low doses of rotenone through the jugular vein for as long as five weeks.
Rotenone is an organic product made from extracts of tropical plants.
It is widely used as an agricultural pesticide and to kill unwanted fish in reservoirs. People most frequently would be exposed to rotenone by ingesting residue in food or by handling the compound. Scientists acknowledged the pump method used in the experiment did not duplicate rotenone exposure in the real world, but said it was a more direct and reliable method for research purposes. Whether the pesticide would have the same effect in people via normal routes of exposure is not clear. Greenamyre said half of the rats gradually showed Parkinson's symptoms.