Bullies are no match for gene knockout

After repeated harassment by larger, more aggressive members of their species, mice withdraw from social contact, exhibiting behavior that is strikingly similar to that seen in humans with depression, social phobia and post-traumatic stress disorder.

Using a video system that creates a map of a mouse’s movements, Assistant Professor of Psychiatry Ralph J. DiLeone, Ph.D., and colleagues found that a normal mouse (white trail in left panel) will frequently interact with another mouse placed at one side of its enclosure, but a mouse “defeated” by aggressors (black trail) will shy away.

Pleasurable social experiences activate reward pathways in the brain that are also stimulated by drugs of abuse, so the team wondered whether this socially withdrawn behavior might be governed by those same circuits.

As reported in the February 10 issue of Science, when the scientists selectively shut down the gene for a protein known as BDNF in an important brain reward center, mice did not develop social withdrawal in response to aggression, suggesting that BDNF in the reward pathway may be a fruitful target for new psychiatric drugs.