Stress during adolescence can cause postpartum behavioural changes in women and other mammals, including depression and changes in social behaviour after the birth of a child. Researchers from the University of Alabama at Birmingham used a mouse model to show how psychological stress during adolescence alters neuronal functions in the brain, resulting in altered postpartum social behaviour.
This research builds on their recent finding that mice exposed to social isolation in late adolescence, which alone causes no endocrine or behavioural changes, show long-lasting behavioural changes only when accompanied by pregnancy and delivery.
The team used this behavioural model to probe for postpartum neural circuit differences between mouse dams that were stressed in late adolescence and a control group of mouse dams that remained unstressed in adolescence, due to normal social interactions with other mice.
They focused on the prelimbic cortex -- a hub region of the brain that plays a crucial role in social behaviour and regulation of stress responses. In the study, published in the journal Nature Communications, the researchers found that adolescent psychosocial stress, combined with pregnancy and delivery, caused hypofunction of the glutamatergic pathway that they mapped from the anterior insula region of the brain cortex to the prelimbic cortex.
Glutamate is the main excitatory neurotransmitter in the central nervous systems of mammals. The diminished function of this cortico-cortical pathway altered neuronal activity in the prelimbic cortex and led, in turn, to abnormal social behaviour, as seen in a test of how much time a mouse dam spends with a familiar mouse that is confined in one corner of a cage, versus a novel mouse, confined in another corner.
"These findings suggest that the prolonged elevation of the stress hormone during the postpartum period plays a crucial role in the observed alterations in neuronal pathway and social behaviour," said Minae Niwa from UAB's Department of Psychiatry and Behavioral Neurobiology.
"Our study has revealed significant findings that demonstrate the involvement of the anterior insula-prelimbic pathway in adolescent stress-induced postpartum alterations related to the recognition of the novelty of other mice, which is a key aspect of social behaviour," she said.