Chen et al. [141] showed that the overexpression of the hippocampal FXR could reduce the expression of BDNF in naïve rats, Hu et al.’s [140] study found that the FXR–CREB interaction and the CRTC2 cytoplasmic translocation in the CA1 region were essential for depression, which was confirmed by the use of the hippocampus-specific FXR-null mice. The gene discussed is NR1H4; the disease is major depressive disorder.