| The root of Paeonia lactiflora Pall. (Family: Ranunculaceae), commonly known as peony, is a component herb of many traditional formulae for the treatment of depression-like disorders. Previous studies have demonstrated the antidepressive effect of peony extract in mouse models of depression. Total glycosides of peony (TGP) is regarded as the major active ingredients of peony. The present study aims to confirm the antidepressive potential of TGP and evaluate its action mechanisms.;The antidepressant-like effect of TGP was firstly evaluated by the behavioral despair test, forced swim test and tail suspension test. The results showed that intragastric administration of TGP caused a significant reduction of immobility time in both forced swim and tail suspension tests in mice. TGP treatment also significantly reduced the duration of immobility time in the forced swim test in rats.;Secondly, the antidepressant-like effect of TGP was evaluated by a rat model of depression induced by chronic unpredictable mild stress (CUMS). The results showed that a 5-week CUMS caused depression-like behavior in rats, as indicated by a significant decreases in sucrose consumption (assessed by sucrose preference test) and locomotor activity (assessed by open-field test), and an increase in immobility time (assessed by forced swim test). Intragastric administration of TGP during the five weeks of CUMS procedure significantly suppressed these behavioral changes induced by CUMS.;Thirdly, the neuroprotective effects of TGP on CUMS-treated rats and its possible mechanisms were investigated. The results showed that treatment with TGP for 5 weeks produced neuroprotective effects on the hippocampus of CUMS-treated rats. This effect was associated with the attenuation of hypothalamic-pituitary-adrenal axis hyperactivation (characterized by a decreased serum corticosterone level and an increased hippocampal glucocorticoid receptor expression), an inhibition of oxidative stress, and up-regulation of neurotrophins such as brain-derived neurotrophic factor and neurotrophin-3 in the hippocampus.;Finally, the neuroprotective effects of TGP against corticosterone-induced neurotoxicity in rat pheochromocytoma (PC12) cells, an in vitro experimental model of depression were studied. The results showed TGP treatment dose-dependently protected the cells against corticosterone-induced toxicity. The cytoprotection afforded by TGP treatment was shown to be associated with an enhanced antioxidant activity, and increased expressions of neurotrophins including brain-derived neurotrophic factor, nerve growth factor and neurotrophin-3.;Taken together, the results confirmed the antidepressant-like effect of TGP. The antidepressive action of TGP may be mediated by the modulation of the hypothalamic-pituitary-adrenal axis function, the inhibition of oxidative stress, and the up-regulation of neurotrophins, thereby leading to the neuroprotective effects. |
