The FXR is the most prominent BA signaling pathway in neuropsychiatric disorders. In rats, up-regulation of FXR in the hippocampus is appeared to be involved in depression-like symptoms and reduced BDNF levels. Some anti-depressants, including paroxetine, has the ability to modify the gut microbiome and BA synthesis in mice. The gene discussed is NR1H4; the disease is depressive symptom measurement.