NTF4 and major depressive disorder: However, the therapeutic effects of VD3 on the chronic unpredictable mild stress (CUMS) model of depression, and whether the antidepressant-like action of VD3 involves BDNF, neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and the HPA axis in long-term OVX adult rats remain unknown.