The regulation of social factors on anxiety and microglial activity in nucleus accumbens of adolescent male mice: Influence of social interaction strategy.

Adolescence is a period characterized by a high vulnerability to emotional disorders, which are modulated by biological, psychological, and social factors. However, the underlying mechanisms remain poorly understood. Combining physical or emotional social defeat stress (PS and ES) and pair or isolation rearing conditions, we investigated the effects of stress type and social support on emotional behavior and central immune molecules in adolescent mice, including anxiety, social fear, and social interaction strategies, as well as changes in microglia-specific molecules (ionized calcium-binding adaptor molecule 1 (Iba1) and a cluster of differentiation molecule 11b (CD11b)) in the medial prefrontal cortex (mPFC), hippocampus (HIP), amygdala (AMY), and nucleus accumbens (NAc). Mice exposed to both physical stress and isolated rearing condition exhibited the highest levels of anxiety, social fear, and microglial CD11b expression in the NAc. In terms of social support, pair-housing with siblings ameliorated social fear and NAc molecular changes in ES mice, but not in PS mice. The reason for the differential benefit from social support was attributed to the fact that ES mice exhibited more active and less passive social strategies in social environment compared to PS mice. Further, the levels of stress-induced social fear were positively associated with the expression of microglial CD11b in the NAc. These findings offer extensive evidence regarding the intricate effects of multiple social factors on social anxiety and immune alteration in the NAc of adolescent mice. Additionally, they suggest potential behavioral and immune intervention strategies for anxiety-related disorders in adolescents. • Stress type and social support displayed distinct effects on anxiety and NAc microglial CD11b of adolescent mice. • Stress-induced social fear was positively associated with the expression of microglial CD11b in the NAc. • Pair-housing with siblings ameliorated social fear and NAc molecular changes in emotionally but not physically stressed mice. • Different benefit from social support was attributed to more active and less passive social strategies in ES than PS mice. • NAc microglial activities and social strategies are involved in effects of social factors on anxiety in adolescents. [ABSTRACT FROM AUTHOR]