In the CUS model, enrichment environment improves depression-like behavior in SPT, FST, and OFT by regulating rat hippocampal microglia phenotype (decreasing the M1-type marker iNOS and increasing the M2-type marker CD206), inhibiting NF-κB activation and upregulation of pro-inflammatory cytokines (Li Y. et al., 2022). Here, MRC1 is linked to major depressive disorder.