Antidepressant-like effects of standardized gypenosides: involvement of brain-derived neurotrophic factor signaling in hippocampus.

ABSTRACT

RATIONALE Gypenosides have been reported to produce neuroprotective effects and increase monoamine neurotransmitter levels in the brain. OBJECTIVE: Considering that depression is involved in monoamine reduction, this study evaluated the antidepressant-like effects of gypenosides in mice exposed to chronic unpredictable mild stress (CUMS). METHODS: The sucrose preference test and forced swimming test were performed after administration of gypenosides (at 25, 50, or 100 mg/kg) for 4 weeks. Hippocampal brain-derived neurotrophic factor (BDNF) and its downstream targets were analyzed by western blot. Additionally, hippocampal neuronal proliferation was measured by immunohistochemistry. RESULTS: Four-week treatment with fluoxetine (20 mg/kg) and gypenosides (at either 50 or 100 mg/kg) increased sucrose preference and decreased the immobility time in mice exposed to CUMS. In addition, gypenosides (at either 50 or 100 mg/kg) also increased BDNF expression and neuronal proliferation in the hippocampus of CUMS animals. Further, we showed that treating CUMS mice with K252a, which is an inhibitor of the BDNF receptor TrkB, blocked the effects of gypenosides (100 mg/kg), including behavioral improvements, neuronal proliferation, and up-regulation of p-TrkB, p-ERK, and p-Akt proteins. CONCLUSIONS: This study demonstrates that gypenosides exhibit antidepressant-like effects in mice, which may be mediated by activation of the BDNF-ERK/Akt signaling pathway in the hippocampus.