Juvenile chronic social defeat stress reduces prosocial behavior in adult male mice.

Exposure to stress in early life can have a significant impact on individuals. However, the effects of early-life stress (ELS) on prosocial behavior remain unclear, as do the underlying mechanisms. In this study, ICR juvenile mice were subjected to juvenile chronic social defeat stress (jCSDS) between postnatal days 32 and 41, during which body weight changes were continuously monitored. The behaviors of adult mice were evaluated using the open field test (OFT), the social interaction test (SIT), and the prosocial choice task (PCT). ELISA was used to quantify serum levels of oxytocin, serotonin, and dopamine. The density of dendritic spines in the basolateral amygdala was evaluated by Golgi staining. Behavioral test results showed that jCSDS induced anxiety-like behavior and decreased prosocial selection tendency in mice. Additionally, exposure to jCSDS increased the serum levels of oxytocin, decreased those of serotonin, and increased the density of dendritic spines in the basolateral amygdala. Correlation analysis indicated that prosocial behavior was negatively correlated with serum oxytocin levels and dendritic spine density in the basolateral amygdala. These results suggested that jCSDS reduced prosocial behavior, possibly due to changes in serum oxytocin contents and adaptive changes in amygdaloid neurons.