With the new the study, researchers examined a group of neurons in the brains of mice. During the study they subjected the animals to a variety of "highly stressful" situations. For instance, the mice received painful electric shocks in their feet, which mimicked the conditions they face under uncontrollable and inescapable stress. The animals were then allowed to escape the shocks.
The mice,
Nature News reports, were then examined to see which ones showed stress resilience and which ones had become helpless and depressed. In the tests, it was found that about 22 percent of the mice displayed helpless, depressed behaviors. Most noticeably, these mice did not try to escape the shocks even though they could. The researchers found that in these depressed mice, neurons in a brain region called the medial prefrontal cortex had become highly excited and active.
Looking at this further, the same neurons were weakened in the resilient mice that seemed unaffected by stress. Therefore, the findings suggest that higher activity in the medial prefrontal cortex is linked to poor behavioral responses to stress, and may underlie depression.
Looking at this further, and to find out whether depression boosted activity in the medial prefrontal cortex or if the increased activity in that brain region led to depression, the researchers engineered mice to mimic the neuronal conditions they found in depressed mice. The results, according to the
research brief, showed that once-strong and resilient mice became helpless, showing all of the classic signs of depression.
The longer term aim of the study is to find a precise target in an experimental treatment for depression. The study has been published in
The Journal of Neuroscience. The
research is titled "Synaptic Modifications in the Medial Prefrontal Cortex in Susceptibility and Resilience to Stress."
