The researchers found that a single stressful incident can lead to increased electrical activity in a brain region known as the amygdala. This activity sets in late, occurring ten days after a single stressful episode and is dependent on a molecule known as the N-Methyl-D-Aspartate Receptor (NMDA-R), an ion channel protein on nerve cells known to be crucial for memory functions.
The amygdala is a small, almond-shaped groups of nerve cells that is 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), a mental condition that develops in a delayed fashion after a harrowing experience.
Previously, researchers had shown that a single instance of acute stress had no immediate effects on the amygdala of rats. But ten 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,” said lead study author Sumantra Chattarji from the National Centre for Biological Sciences (NCBS) in Bangalore.
“We know that the amygdala is hyperactive in PTSD patients. But no one knows as of now, what is going on in there,” he added.
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. However, until now, the physiological effects of these new connections were unknown.
Chattarji’s team has established that the new nerve connections in the amygdala lead to heightened electrical activity in this region of the brain.
“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,” Chattarji stated.