BDNF and depressive symptom measurement: Serum corticosterone levels, depression-like behavior, and hippocampal pathophysiology, including the expression of brain-derived neurotrophic factor (BDNF), precursor BDNF (proBDNF), doublecortin (DCX), NeuN, glial cell activation, and tumor necrosis factor-α (TNF-α), were examined.