VGF and major depressive disorder: VGF expression in the hippocampus is decreased in mouse models of depression-like behavior and in postmortem samples of hippocampus and Brodmann area 25 from both medicated and unmedicated male and female patients with MDD compared to controls (Jiang et al., 2018, 2019a), while expression is increased by exercise and chronic antidepressant treatment, including fluoxetine and ketamine (Hunsberger et al., 2007; Thakker-Varia et al., 2007; Jiang et al., 2018, 2019a).