Exercise may boost brain's natural antidepressant

By Amy Norton

NEW YORK (Reuters Health) - Exercise seems to increase the production of naturally occurring brain chemical with antidepressant effects in mice, researchers reported Sunday.

The findings, published in the journal Nature Medicine, point to potential new ways to treat depression in people.

Studies have found that exercise can help ease depression symptoms, but the reasons for the benefit have not been clear. For the new study, scientists used a tool called a microarray to examine how exercise changed gene activity in the brains of mice.

They focused on a brain region known as the hippocampus, which has been implicated in mood regulation and in the brain's response to antidepressant medication.

The researchers found that mice that had a week's worth of workouts on a running wheel showed altered activity in a total of 33 genes, the majority of which had never been identified before.

In particular, exercise enhanced activity in the gene for a nerve growth factor known as VGF. Nerve growth factors are small proteins important in the development and maintenance of nerve cells.

Moreover, when the researchers infused a synthetic version of VGF into the brains of the mice, it produced a "robust antidepressant effect" in standardized tests of animals placed in stressful situations.

"The major finding is that we have identified a key factor that underlies the antidepressant effects of exercise -- information that could be used for the development of novel therapeutic agents," said senior researcher Dr. Ronald S. Duman of Yale University in New Haven, Connecticut.