| The herb, as a crucial medicine with little toxicity and side effect in disease therapies and preventions, comes from nature and has unique pharmacological function. Centella asiatica is widely used in Indian herbal medicine, it has many preventative and therapeutic values to many clinical diseases. As one of widely used metal, aluminum has close contact with people's life, many studies indicated that aluminum has toxic effect to human health. In this study, by using electrophysiological, behavioral and biochemical test, we study the effects of madecassoside (MC) on chronical aluminum exposed rats. The results are as follows:(1) MC can, to some extent, repair the synaptic plasticity deficiency induced by aluminum exposure. In our experiments, Wistar rats were treated with chronic low-dose aluminum exposure during the whole lifespan from embryonic period to adulthood, and taken different doses of MC (30, 60, 120mg/kg) by intragastric administration simultaneously once a day. Electrophysiological recordings were performed when the rats were adult. Our results show that, Input/Output (I/O) curve, Paired Pulse Ratio (PPR) and Long Term Potentiation (LTP) of dentate gyrus (DG) in hippocampus are all depressed significantly after chronic aluminum exposure, indicating that chronic low-dose aluminum exposure can impair both basic transmission efficacy and synaptic plasticity. All doses of MC can repair the synaptic plasticity damage induced by chronic aluminum, except that the PPR of 120mg/kg group which has no significant difference with aluminum exposure group.(2) We treated another groups of animals in the same way with lessen period treatment of aluminum and MC. The rats should survive for another 20 days after drugs were canceled one month after lactation, we performed the Morris water maze experiment and assayed the oxidative stress. Results show that the 30, 60mg/kg MC groups have a shorter escape latency than aluminum exposure group, in contrast, the 120mg/kg group has no significant difference. Treated with different doses of MC can shorten the escape latency of control group significantly. During the probe test, 60mg/kg group can shorten the latency entering the plate quadrant after aluminum exposure. Compared with control, 120mg/kg group had a shorter latency entering the plate quadrant. In addition, after treated with different doses of MC, there were no obvious effects on the time stayed in the plate quadrant and the frequency crossing the plate of controls and aluminum exposed group. All of our results suggested that, MC can improve the spatial learning and memory ability of rats to a certain extent. In addition, we assayed related oxidative stress of these groups of animals, it is indicated that all groups have no significant differences in the SOD activity and GSH content, the aluminum exposure together with 30mg/kg MC treated group has a lower MDA content than aluminum treated group, which illustrates that, 30mg/kg MC can decrease lipid peroxidation to some extent. However, no obvious differences are found in other groups. So, we suppose that the repairment of synaptic plasticity deficiency of aluminum exposure induced by MC is not duing to oxidative stress.All above data indicated that, under the circumstance of aluminum exposure together with a shorter time MC treatment, and then stopped aluminum exposing and drug apply for a span, rats'poisoning symptoms were not obvious, we suppose that the in vivo accumulations of both aluminum and MC decrease, as a result, MC seems to have ability of improving memory.Our results suggest preliminarily MC's repairment of learning and memory deficiency of chronic aluminum exposure. |
