In Parkinson's, cells in the brain that contain dopamine, a neurotransmitter essential for purposeful and facile muscle control, progressively die until only a small percentage remains. Dopamine carries signals from the nerve cells, or neurons, located deep inside the brain in an area called the substantia nigra along nerve fibers that end in the brain's striatum, an area involved in control of movement. In the absence of dopamine, neurons can't send the appropriate messages for smooth motor control, resulting in the telltale symptoms of Parkinson's: uncontrollable tremors, rigidity of limbs, slow movements and stooped posture.
In one of the studies presented by Annie D. Cohen, a doctoral student in the department of neurology and Center for Neuroscience at the University of Pittsburgh School of Medicine, the researchers examined the brains of rats that had been forced to exercise for seven days before receiving a toxin that normally induces Parkinson's disease. They found that, compared to animals that had not been exercised, significantly fewer dopamine-containing neurons died.
"Whereas a number of explanations could be offered as to why the exercised animals do so well, we have evidence that indicates it's because exercise stimulates production of key proteins that are important for survival of neurons," said the study's senior author, Michael J. Zigmond, Ph.D., professor of neurology, neurobiology and psychiatry, and co-director of the Parkinson's Disease Center of Exce