BDNF and major depressive disorder: It should be noted that not only the hippocampus is implicated in the pathophysiology of depression as BDNF protein is increased in the frontal cortex of rats after treatment with different monoaminergic antidepressants (Balu et al. 2008; Calabrese et al. 2010, 2007; Cooke et al. 2009; Hodes et al. 2010; Mannari et al. 2008).