Exercise helps brains bounce back

Study of rhesus monkeys shows running protects dopamine neurons from death

CHICAGO — A toned, buff bod isn’t the only thing a workout is good for. Exercise protects special brain cells in monkeys’ brains and improves motor function, a new study finds. The data, presented at a news briefing October 18 in Chicago at the Society for Neuroscience’s annual meeting, adds to a growing body of evidence that shows exercise is good for the brain, too.

“This is sort of a quiet revolution that’s been occurring in neuroscience,” says Carl Cotman, a brain aging expert at the University of California, Irvine, “to realize that physical activity at a certain level impacts the brain in a really profound way.”

In the new study, researchers led by Judy Cameron of the University of Pittsburgh trained six adult female rhesus monkeys to run on treadmills built for humans. Over a period of three months, monkeys either ran, jogged or sat on a treadmill for five hours each week. Monkeys that ran got their heart rates to about 80 percent of maximum, comparable to a human training program that would increase cardiovascular fitness. The jogging monkeys’ heart rates reached about 60 percent of maximum.

After this training period, the researchers hit the right side of the monkeys’ brains with a neurotoxin called MPTP, designed to selectively kill neurons that produce the signaling chemical dopamine. These neurons, and the dopamine they produce, regulate movement, and are the very same ones that die in people with Parkinson’s disease.

Sedentary monkeys showed the expected decrease in these dopamine neurons on the right side of the brain after the neurotoxin was applied. But in the brains of monkeys that had run for the past three months, the neurotoxin had almost no effect. In the runners, dopamine neurons were just as plentiful on the right side of the brain as on the left.

Jogging also had a protective effect, although slightly weaker than running’s, Cameron says. “This is really good news. It means that any little bit more activity you can do is positive for your brain,” says Cameron. “Your brain seems very sensitive to exercise.”

When the researchers continued the experiment for another six weeks, the results held. A brain scan revealed that “the animals that were exercising had virtually no loss of dopamine in those neurons,” Cameron says. “We think that exercise is very neuroprotective.”

Next, the researchers assessed the monkeys’ ability to use the hand affected by the neurotoxin. Monkeys had to retrieve a Lifesaver candy from a thin wire, an experiment designed to test motor coordination. Sedentary monkeys could not use their left, affected hand at all, while the runners showed no difference between their left and right hands, the researchers found.

The new study highlights the importance of exercise for maintaining a healthy brain. Other studies presented at the meeting have found that exercise has a wide range of brain-protective roles in mice, monkeys and humans.

Laura Sanders is the neuroscience writer. She holds a Ph.D. in molecular biology from the University of Southern California.

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