Exercise may boost brain's natural antidepressant

Exercise may boost brain's natural antidepressant
Amy Lottes, left, works out at the YMCA with the help of her personal trainer, Gina Pona-Norton, Wednesday, Nov. 21, 2007, in Kirkwood, Mo. Exercise and portion control have helped Lottes keep off the weight she lost four years ago with the help of a nutritionist and personal trainer and this Thanksgiving, she plans to forfeit dessert and second helpings and have a second glass of wine instead. (AP Photo/Whitney Curtis)NEW YORK (Reuters Health) - Exercise seems to increase theproduction of naturally occurring brain chemical withantidepressant 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 depressionsymptoms, but the reasons for the benefit have not been clear.For the new study, scientists used a tool called a microarrayto examine how exercise changed gene activity in the brains ofmice.
They focused on a brain region known as the hippocampus,which has been implicated in mood regulation and in the brain'sresponse to antidepressant medication.
The researchers found that mice that had a week's worth ofworkouts on a running wheel showed altered activity in a totalof 33 genes, the majority of which had never been identifiedbefore.
In particular, exercise enhanced activity in the gene for anerve growth factor known as VGF. Nerve growth factors aresmall proteins important in the development and maintenance ofnerve cells.
Moreover, when the researchers infused a synthetic versionof VGF into the brains of the mice, it produced a "robustantidepressant effect" in standardized tests of animals placedin stressful situations.
"The major finding is that we have identified a key factorthat underlies the antidepressant effects of exercise --information that could be used for the development of noveltherapeutic agents," said senior researcher Dr. Ronald S. Dumanof Yale University in New Haven, Connecticut.
Exercise "clearly has effects on the brain," he toldReuters Health, and they are both direct and indirect. It'spossible, he explained, that the current findings reflect adirect effect of exercise on nerve cells in the hippocampus, ormore general changes in the brain, like better blood flow orincreased hormonal activity.
Besides offering more support for the benefits of exercise,the findings also point to VGF as a target for newantidepressants, according to Duman and his colleagues. Suchmedications, they point out, would work by an entirelydifferent mechanism than existing antidepressants, which areeffective for about 65 percent of patients.
SOURCE: Nature Medicine, online December 2, 2007.