The total flavonoids extracted from Xiaobuxin-Tang up-regulate the decreased hippocampal neurogenesis and neurotrophic molecules expression in chronically stressed rats

Xiaobuxin-Tang (XBXT), a traditional Chinese herbal decoction, has been used for the treatment of depressive disorders for centuries in China. Our previous studies have demonstrated that the total flavonoids (XBXT-2) isolated from the extract of XBXT reversed behavioral alterations and serotonergic dysfunctions in chronically stressed rats. Recently, accumulating studies have suggested the behavioral effects of chronic antidepressants treatment might be mediated by the stimulation of hippocampal neurogenesis. In present study, we explored the effect of XBXT-2 on hippocampal neurogenesis and neurotrophic signal pathway in chronically stressed rats. Our immunohistochemistry results showed that concomitant administration of XBXT-2 (25, 50 mg/kg, p.o., 28 days, the effective doses for behavioral responses) significantly increased hippocampal neurogenesis in chronically stressed rats. Four weeks after BrdU injection, result in double immunofluorescence labeling showed that some of the newly generated cells in hippocampus co-expressed with NSE or GFAP, markers for neurons or astrocytes, respectively. Furthermore, XBXT-2 treatment reserved stress-induced decrease of hippocampal BDNF and pCREB (Ser133) expression, two important factors which were closely related to hippocampal neurogenesis. As a positive control drug, imipramine (10 mg/kg, p.o.) exerted same effects. In conclusion, the increase of neurogenesis, as well as expression of BDNF and pCREB in hippocampus may be one of the molecular and cellular mechanisms underlying the antidepressant action of XBXT-2.