Antidepressant-like effects of tea polyphenols on mouse model of chronic unpredictable mild stress

Tea polyphenols (TPs), which are the natural compounds extracted from tea leaves, possess a number of beneficial properties, such as reducing the risks of cancer and heart diseases, alleviating cognitive impairments and showing antidepressant-like activity in the forced swim test (FST) and tail suspension test (TST). The present study was designed to investigate the protective effect of TPs on the chronic unpredictable mild stress (CUMS)-induced depression model in mice and to elucidate the related underlying mechanisms. With the daily exposure to stressor for 5 consecutive weeks, TPs were administered in mice at a daily dose of 25 mg/kg or 50 mg/kg by gavage for 3 consecutive weeks from the 3rd week. Our results showed that CUMS significantly decreased the levels of serum serotonin (5-HT) and norepinephrine (NE) in the hippocampus, the prefrontal cortex and serum, and the activities of superoxide dismutase (SOD) and catalase (CAT), with an increase in lipid peroxidation level as well as a reduction in glutathione (GSH) level and an elevation in the production of malondialdehyde (MDA) in the hippocampus and the prefrontal cortex. CUMS also reduced open-field activity, sucrose consumption, as well as increased immobility duration in FST and TST. TPs administration could effectively reverse the alterations in the concentrations of 5-HT and NE, elevate the activities of SOD and CAT as well as the level of GSH, reduce the MDA level and inhibit lipid peroxidation. Moreover, TPs could effectively reverse alterations in immobility duration, sucrose consumption and open-field activity. In conclusion, TPs administration has exhibited significant antidepressant-like effects in mice with CUMS-induced depression. The antidepressant activity of TPs might be related to the alteration of monoaminergic responses and antioxidant defenses.