BDNF and major depressive disorder: Similarly, VGF was found to be downregulated in the hippocampus in animal models of depression and human bipolar disorder, and previous studies have demonstrated that increasing levels of the VGF-derived C-terminal peptide TLQP-62 results in antidepressant-like behavioral effects in mice [23,24] in a manner that is dependent on BDNF/TrkB/CREB signaling [25].