The antidepressant-like effects of Chaihu Shugan San: Dependent on the hippocampal BDNF-TrkB-ERK/Akt signaling activation in perimenopausal depression-like rats.

Abstract

Chaihu Shugan San (CSS), a traditional Chinese medicine formula, has been used to treat depression for hundreds of years. Recently, the antidepressant-like mechanism of CSS has been increasingly evaluated and demonstrated. However, there are few studies focused on the involvement of the neurotrophic system in mediating the antidepressant-like effects of CSS. Considering the high prevalence of perimenopausal depression around the world, the goal of the present study was to determine whether brain-derived neurotrophic factor (BDNF) signaling is required for the antidepressant-like effects of CSS in perimenopausal depressive-like rats. The results indicate that CSS reverses depressive-like behaviors and attenuates the downregulation of BDNF in the hippocampus of perimenopausal rats exposed to chronic unpredictable mild stress (CUMS). We found that the TrkB antagonist K252 not only blocks the effects of CSS on behavioral improvement but also abolishes the activation of CSS in BDNF-TrkB signaling. As a result, the downstream targets of BDNF signaling, such as the ERK and Akt pathways, are significantly inhibited by K252a. Furthermore, CSS increases hippocampal neurogenesis, while K252a fully prevents this action. In conclusion, the present results demonstrate that the activation of the hippocampal BDNF-TrkB-ERK/Akt signaling pathway is required for the antidepressant-like effects of CSS on the depressive-like state during perimenopause. Additionally, this study also demonstrates that neurogenesis is required for the effects of antidepressants in aging perimenopausal animals and provides fundamental evidence for the clinical application of CSS.