AsianScientist (Jan. 11, 2017) – A single stressful incident can lead to increased electrical activity in the amygdala, a region of the brain is known to play key roles in emotional reactions, memory and making decisions. These findings, published in Physiological Reports, shed light on how traumatic events can have long-term psychological repercussions.
Changes in the amygdala are linked to the development of post-traumatic stress disorder (PTSD), a mental condition that develops in a delayed fashion after a harrowing experience. Previously, a team led by Professor Sumantra Chattarji from the National Centre for Biological Sciences had shown that a single instance of acute stress had no immediate effects on the amygdala of rats. However, these animals began to show increased anxiety and changes in the architecture of their brains ten days later.
Closer investigation 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. However, until now, the physiological effects of these new connections were unknown.
In the present recent study, Chattarji’s team has established that the new nerve connections in the amygdala lead to heightened electrical activity in this region of the brain.
“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 Ms. Farhana Yasmin, one of Chattarji’s students and first author of the study. “So, our work is unique in that we show a reaction to a single instance of stress, but at a delayed time point.”
Furthermore, the researchers also showed that blocking a protein involved in memory and learning called the NMDA receptor during the stressful period not only stopped the formation of new synapses, but also blocked the increase in electrical activity at these synapses.
“So we have for the first time, a molecular mechanism that shows what is required for the culmination of events ten days after a single stress,” said Chattarji. “In this study, we have blocked the NMDA receptor during stress. But we would like to know if blocking the molecule after stress can also block the delayed effects of the stress. And if so, how long after the stress can we block the receptor to define a window for therapy,” he added.
The article can be found at: Yasmin et al. (2016) The Delayed Strengthening of Synaptic Connectivity in the Amygdala Depends on NMDA Receptor Activation During Acute Stress.
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Source: National Center for Biological Sciences.
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