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New insights on how the brain responds to stress

Scientists at the National Center for Biological Sciences and the Institute for Stem Cell Biology and Regenerative Medicine in Bangalore have revealed how a single stress event may result in a long lasting psychological trauma. The research team led by Professor Sumantra Chattarji has been able to identify key mechanisms and changes in molecular and physiological processes that have an impact on the brains architecture.

Results have shown that a single stressful event leads to increased electrical activity in the region of the brain known as the amygdala, an almond shaped structure located deep in the temporal lobe, and is a crucial component in processing memory and emotional reactions. The stimulation of the amygdala results in an intense emotional response such as aggression and fear, and through its connection to the hypothalamus, affects blood pressure, heart rate and breathing.

The study which was performed on rats has demonstrated that acute stress occurrences have no immediate impact on the amygdala, but that changes become observable within 10 days. This delayed effect is highly dependent on the activation of N-Methyl-D-Aspartate receptors (NMDA-R) found on nerve cells. These ion channels regulating electrical flow are an essential element in forming long and lasting memories by allowing changes of the brain’s architecture. In days following a high stress occurrence, the hyperactive amygdala forms new neural connection in that specific region, resulting in a heightened electrical activity. Until now, it remained unclear how the activation of NMDA receptors acted on brain plasticity to form neural pathways. In the experiment, Professor Sumantra Chattarji’s team blocked NMDA-R during an induced traumatic episode and has demonstrated a significant reduction of anxiety and stress in rats.

A hyperactive amygdala is often observed in patients suffering from post-traumatic stress disorders (PTSD), a mental condition that develops following an intensely stressful experience. Mr Chattarji said: “We have, for the first time, a molecular mechanism that shows what is required for the culmination of events 10 days after a single stress”

Blocking NMDA receptors following high levels of stress could prove successful in preventing future psychological disorders. Yet Mr. Chattarji acknowledges the danger of such treatments as it is not clear how preventing certain memories can affect overall behavior.

“Since NMDA receptors are needed for forming memories, a generic blocking will indeed be a problem. That is why we cannot simply block this receptor in anticipation of a traumatic experience, because that may impair the formation of other memories as well. However, at the time of the trauma, having the blocker on board would help prevent that experience from becoming of the source of subsequent emotional symptoms in the amygdala. So, it is a fine balance” said Mr. Chattarji

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