Researchers in the U.S. say that deleting a specific gene in the brain of mice that have been conditioned to be depressed, has the same effect as antidepressants.
Dr. Eric Nestler, chairman of psychiatry at the University of Texas Southwestern Medical Center and the study's senior author, says that disabling a memory molecule in the brain lifts depression in mice as effectively as using antidepressants.
It seems the depressed mice became more sociable when researchers deleted a memory molecule from their brains; scientists say they believe the finding might help treat human conditions such as social phobia and post-traumatic stress.
According to Dr Olivier Berton the report's lead author, they targeted a molecule in a section of the brain known to be related to sensations of pleasure and danger, often called the reward pathway, which has been studied in relation to drugs that are abused.
Deleting the molecule from this part of the brain meant that the mice were never depressed and fearful, Berton says, even though conditions were set up that normally would make them run and hide.
Mice are normally considered to be social animals, easily approaching and greeting unfamiliar mice.
But it seems that when strange mice are aggressive, a mouse over time becomes timid and withdrawn.
Giving the timid mice antidepressants such as Prozac improves their behavior, but so does deleting a gene called BDNF, which helps regulate the release of the neurotransmitter dopamine, a key substance that carries signals from one nerve cell to another, in the brain's reward pathway.
Dr. Nestler and his colleagues exposed mice to daily bouts of "social defeat," in which they encountered aggressive mice that overcame them in fights.
This training went on for 10 days.
The mice eventually became "defeated," no longer approaching unfamiliar mice, and four weeks later, the defeated mice still avoided other mice, not only their former bullies but even smaller and more docile mice.
However when given the antidepressant drugs Prozac or Tofranil, the defeated mice's social interaction improved.
Dr. Nestler says the important point is that the antidepressant worked over a long period, not just short-term, thus resembling human treatment.