BDNF and major depressive disorder: Thus, the PDK1/Akt pathway has been reported as intermediating in the role of neurotropic factors, like brain-derived neurotrophic factor (BDNF), in the acquisition of fear and mood disorders like depression and anxiety (Chen et al., 2006; Duman and Monteggia, 2006; Ou and Gean, 2006; Martinowich et al., 2007).