Could Our Responses to Stressful Situations Be Biological?

People respond to stressful situations like bullying in different ways. Scientists at the Advanced Science Research Center at The Graduate Center, CUNY, and Hunter College have uncovered biological differences in mice that could help explain this variation in humans. The study, published in eLife, could help lead to new treatments for mental disorders.

The study’s researchers and co-authors included Valentina Bonnefil, Mario Amatruda, Maureen Wentling, Gary Temple, Hye-Jin Park, and Professors Patrizia Casaccia and Jia Liu, all from CUNY ASRC; Antonio Aubry and Professor Nesha Burghardt from Hunter; along with colleagues from the Icahn School of Medicine and Virginia Commonwealth University.

The researchers allowed test mice to have a five-minute encounter with an aggressive mouse every day, for a total of 10 days. After this period, they watched how this stressful experience impacted the sociability of the test mice by exposing each of them to a novel, non-aggressive mouse. While some test mice displayed normal “social behavior” and were interested in sniffing the new mouse, others seemed to be negatively affected by the previous aggressive experience, and avoided interaction.

The scientists looked at different brain regions involved in regulation of social behavior to identify changes that could distinguish between these two groups of mice. They found that mice who were more susceptible to the effects of the aggressive encounter had thinner myelin sheaths—the fatty coating that protects nerves—around their neurons, and shorter myelin segments in a brain area called the medial prefrontal cortex. They also had fewer mature oligodendrocytes, the type of cells that form the myelin sheath.

The researchers found evidence that in the susceptible mice, the genes in charge of oligodendrocyte maturation were more likely to be turned off. In other words, stressful events may affect genes in these animals, causing biological changes that result in socially isolating behavior.

This mechanism, Casaccia said in an interview with CUNY ASRC, “may account for the increased susceptibility to developing chronic psychiatric disorders in some individuals … Current treatments target neuronal function, but Dr. Liu’s work identifies glial cell dysfunction as potential target for future investigation in the treatment of mood disorders.”