Therefore, in a group of mice already submitted to a behavioral test of depression [26], we examined the expression of some neurotrophic/growth factors associated with the pathogenesis of depressive disorders, such as BDNF, IGF-1, nerve growth factor (NGF), and fibroblast growth factor 2 (FGF-2) [30,31,32,33]. This evidence concerns the gene BDNF and major depressive disorder.