The Effects Of EGCG On Hippocampal Learning And Memory Defect Caused By Lead Or Depression

As an important polyphenol in green tea, Epigallocatechin gallate (EGCG) can reach the brain through the blood-brain barrier and plays a great role as antioxidants and metal chelators. Recent studies have focused on the effects of EGCG on the malignant diseases (including neurodegenerative diseases, cancer and cardiovascular diseases and so on), and it greatly attracted peoples'attention.Using two animal models, the developmental lead-exposed and forced-swimming rats, we first study the effects of EGCG on the impairment of synaptic plasticity in developmental lead-exposed rats. Then we study the possible role of EGCG on the behavior and synaptic plasticity in forced-swimming depression rats.On the first study, we found that EGCG can significantly improve the performance of rats in the Morris water maze. When compared with the lead group, EGCG significantly reduced the escape latency in the navigation test, and increased the time of rats crossing the original platform in the probe trial. Meanwhile, EGCG partly repaired the synaptic plasticity in the DG area of hippocampus impaired by lead exposure. Compared with the control group, EGCG enhanced the efficacy of basal synaptic transmission and long-term potentiation of fEPSP slope and PS amplitude.By forced-swimming test, we successfully established the model of depression, as the sugar consumption was decreased in forced-swimming rats. We found that EGCG can eminently improve the percent of sugar consumption in the model of depression. Compared with the control group, EGCG treated rats significantly decreased the immobility time and delayed the first immobility appearance. In the open-field test, the EGCG treated rats increased the number of grid crossing, the time in central grid and the number of standing and grooming. Simultaneously, EGCG has a distinguished elevation in the basis of synaptic transmission in the DG area of hippocampus. In the induction of LTP, the effect of EGCG is not obvious. EGCG only has a slight increase in the LTP of fEPSP slope, but in terms of the LTP of PS amplitude, the difference between the EGCG treated group and the control group has no significance.Our results show that EGCG can repair the deficit of learning and memory induced by the lead exposure, and the effect is concentration-dependent, that is, high concentration of EGCG (50mg/kg) has a stronger effect. EGCG alleviated the depression-like behavior in the model of depression induced by forced-swimming test, and increased the basis of synaptic transmission in hippocampal DG area.