ARG1 and major depressive disorder: found that CSDS mice showed higher M1 microglia markers, including iNOS, cluster of differentiation 16 (CD16), CD86, and C-X-C motif chemokine ligand 10, and no significant changes in M2 markers such as arginase-1 (Arg-1) and CD206 in the hippocampus at the transcriptional and protein levels, suggesting that M1 polarization plays a vital role in depression pathogenesis (75).