BDNF and major depressive disorder: Since Nrf2 KO mice showed decreased BDNF-TrkB signaling in the CA3, DG and PFC, we examined whether the TrkB agonist 7,8-DHF43, 44, 45, 46, 47, 48 shows antidepressant effects in depression-like phenotype of Nrf2 KO mice.