Antidepressant-like effects of paeoniflorin on the behavioural, biochemical, and neurochemical patterns of rats exposed to chronic unpredictable stress.

We have previously demonstrated that the total glycosides of peony exert antidepressant-like effects in animal models. Paeoniflorin is the main active glycoside of peony. The purpose of this study was to evaluate the antidepressant-like effects of paeoniflorin in a rat model of chronic unpredictable stress (CUS) and its active mechanisms. The results showed that CUS-exposed rats exhibited depressive-like behaviour with reduced weight, low motor activity as well as reduced consumption of sucrose, biochemical changes with increased concentrations of corticosterone and adrenocorticotropic hormone and neurochemical changes with reduced monoamine neurotransmitter levels. Paeoniflorin treatment markedly increased sucrose consumption and decreased serum corticosterone and adrenocorticotropic hormone levels in the CUS-treated rats. Furthermore, paeoniflorin treatment significantly attenuated CUS-induced reductions in noradrenaline, serotonin and its metabolite 5-hydroxyindoleacetic acid as well as CUS-induced increases in the ratio between the latter two factors. These results suggest that the modulation of the hypothalamic-pituitary-adrenal axis and up-regulation of serotonergic and noradrenergic systems are important mechanisms underlying the antidepressant-like effects of paeoniflorin in CUS-treated rats.