Brain chemical may play key role in anxiety

By Julie Steenhuysen

CHICAGO (Reuters) - A chemical important for brain development may play a role in explaining why some people are genetically predisposed to anxiety and could lead to new treatments, U.S. researchers said on Tuesday.

They said rats bred to be highly anxious had very low levels of a brain chemical called fibroblast growth factor 2 or FGF2 compared with rats that were more laid back.

But when they improved the anxious rats' living conditions, -- giving them new toys to explore, an obstacle course and a bigger cage to live in -- levels of this brain chemical increased and they became less anxious.

"The levels of this molecule increased in response to the experiences that the rats were exposed to. It also decreased their anxiety," Javier Perez of the University of Michigan, whose study appears in the Journal of Neuroscience, said in a telephone interview.

"It made them behave the same way as the rats that were laid back and had low anxiety to begin with," he said.

Injecting the rats with the chemical also made them less anxious, he said.

In a prior study of people who were severely depressed before they died, the team found the gene that makes FGF2 was producing very low levels of the growth factor, which is known primarily for organizing the brain during development and repairing it after injury.

Perez thinks the brain chemical may be a marker for genetic vulnerability to anxiety and depression. But it can also respond to changes in the environment in a positive way, possibly by preserving new brain cells.