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NCBS & inStem presents new insights into how brain responds to trauma
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Nandita Vijay, Bengaluru
December 31 , 2016
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National Centre for Biological Sciences (NCBS) and the Institute for
Stem Cell Biology and Regenerative Medicine (inStem) have gained
insights into how a single instance of severe stress can lead to delayed
and long-term psychological trauma.
The two Bengaluru-based
research centres have indicated that a single stressful incident can
lead to increased electrical activity in a brain region known as the
amygdala. The activity is delayed, occurring 10 days after a single
episode of stress, and is dependent on a molecule known as the
N-Methyl-D-Aspartate Receptor (NMDA-R), a protein on nerve cells known
to be crucial for memory functions.
The work pinpoints key
molecular and physiological processes that could be driving changes in
brain architecture. The amygdala is a small, almond-shaped groups of
nerve cells located deep within the temporal lobe of the brain. This
region of the brain is known to play key roles in emotional reactions,
memory and making decisions. Changes in the amygdala are linked to the
development of Post-Traumatic Stress Disorder (PTSD),.
The NCBS
team led by Prof. Sumantra Chattarji, was represented by Farhana Yasmin
and Kapil Saxena along with Bruce S. McEwen, head, Harold and Margaret
Milliken Hatch Laboratory of Neuroendocrinology, The Rockefeller
University, New York established that the new nerve connections in the
amygdala lead to heightened electrical activity in this region of the
brain.
Furthermore, a well-known protein involved in memory and
learning, NMDA-R has been recognised as one of the agents that bring
about these changes. Blocking the NMDA-R during the stressful period not
only stopped the formation of new synapses, but also blocked the
increase in electrical activity at these synapses.
Previously,
Chattarji’s group had shown that a single instance of acute stress had
no immediate effects on the amygdala of rats. But 10 days later, these
animals began to show increased anxiety, and delayed changes in the
architecture of their brains, especially the amygdala.
“We showed
that our study system is applicable to PTSD. This delayed effect after a
single episode of stress was reminiscent of what happens in PTSD
patients. We know that the amygdala is hyperactive in PTSD patients. But
no one knows as of now, what is going on in there,” said Prof.
Chattarji.
Investigations revealed major changes in the
microscopic structure of the nerve cells in the amygdala. Stress seems
to have caused the formation of new nerve connections called synapses in
this region of the brain.
Prof. Chattarji’s group first began
their investigations on stress affecting the amygdala and other
regions of the brain around 10 years ago. The work required the team to
employ an array of highly specialised and diverse procedures that range
from observing behaviour to recording electrical signals from single
brain cells and using an assortment of microscopy techniques.
“Now
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,”
said Prof. Chattarji.
“Most studies on stress are done on a
chronic stress paradigm with repeated stress, or with a single stress
episode where changes are looked at immediately afterwards, like a day
after the stress,” said Yasmin.
“To do this, we need to use a
variety of techniques and collaborations with experts We acknowledge the
support of Wadhwani Foundation and DBT-DAE for funding this work,” he
added.
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