Social instability alters the topography of adolescent and adult social behavior and amygdala function

Social instability is a prevalent driver of mental health disorders marked by social dysfunction. Instability has an especially detrimental effect on adolescents, who are characterized by increases in social drive and ongoing brain maturation. The basolateral region of the amygdala, in particular, matures throughout adolescence and is sensitive to social stress, playing an important role in regulating adolescent and adult social behaviors. In the BLA, the GluN2B subunit of the NMDA receptor regulates neuronal activity that is crucial for the expression of social behaviors in an age-specific manner. However, it is unclear how social instability may impact BLA function and specific social behaviors that serve as critical indicators for social dysregulation. We use a social instability protocol in rats to quantify the immediate effect on adolescent and adult social behavior and amygdala function. Social instability increases a subset of social behaviors in the play fighting domain in adolescent and adult rats alike. When groups were separated based on instability-driven boxing and pushing, there was a reduction in sociability in low boxing adolescents; however, high boxing adolescents and adults shifted away from social investigation and towards a greater proportion of play-fighting behaviors. These instability-driven behavioral changes were accompanied by a reduction in adult, but not adolescent, BLA GluN2B expression relative to controls. Our results identify specific social behavioral changes after social instability across ages that may be related to changes in amygdala function.