New insight may treat depression better

Do you know why some people find it difficult to cope with stress and, as a result, develop depression and other mood disorders? That could be due to the mechanism of a small group of neurons, reveals a new study.

Researchers have previously been able to identify the part of the brain that controls our response to stress, but did not exactly know how it does so.

Now, a study in mice identifies a small group of neurons that could be responsible.

"How an animal deals with stress is controlled by a part of the brain known as the prefrontal cortex, and the neurons in this part of the brain are known to change in structure and function in response to stressful situations," the researchers said.

To look at the cellular basis of the responses, the scientists subjected the mice to small electric shocks at random intervals to produce stress.

Most of the mice tried to avoid the shocks, but just over one-fifth did not do so. They also started to avoid other animals or failed to choose tasty foods over plain ones - typical signs of depressive behaviour.

The researchers then looked at the animals' brains and found that a specific set of neurons in the prefrontal cortex were easily excitable in depressed mice, but much harder to excite in those resilient to the stress.

Also, artificially increasing the activity of these neurons caused mice that were once resilient to become susceptible to depressive behaviours.

"We were surprised that we were able to see a difference between depressed and resilient animals at the level of synaptic transmission," said Bo Li of Cold Spring Harbour Laboratory in New York.

The mechanism is unlikely to be as simple as enhancing or decreasing activity, Li says.

The results were published in the Journal of Neuroscience.