FOS and depressive disorder: Our data show that chronic administration of 13-cis-RA to adolescent mice induces depression-like behavior but not anxiety-like behavior and increases c-Fos expression levels in the dentate gyrus (DG), one of the classic emotion-related brain regions, suggesting a link between 13-cis-RA-induced depression and the alteration of synaptic transmission or intrinsic membrane properties of dentate granule cells (DGCs).