These findings emphasize the role of metabotropic (GRM5) and ionotropic glutamate receptors (GRIN2B, GRIN2A) in orchestrating microglia-mediated synaptic transmission in MDD, in contrast to PD where microglia exhibit a neuroinflammation phenotype, and the expression of these genes is downregulated. This evidence concerns the gene GRM5 and major depressive disorder.