Saponins In Polygala Enhance Synaptic Plasticity In Alzheimer’s Disease Rats Model

0bjective①To observe the effects of Saponins in Polygala on the vivo hippocampallong-term potentiation of Alzheimer’s disease（AD） model rats, and to prove whether the effectswere dose-dependent.②To observe the effects of Saponins in Polygala on the hippocampalexpression level of NR2A in AD model rats.Methods 32 healthy male Wistar rats were randomly divided into four groups: control group,AD model group, low dose Saponins of Polygala group（12.5 mg/mL），high dose Saponins ofPolygala group（37.5 mg/mL）. AD model rats were made by injecting ibotenic acid（IBO） intothe basal forebrain Meynert nuoleus of aged rats induced by D-gal. Using Electrophysiologicaltechnique LTP was determined by comparing the average field exciatatory postsynapticpotentia（fEPSP） amplitude after high frequency stimulation（HFS） with that of baseline period.The expression level of NR2A in the hippocampal CA₁region was measured byImmunohistochemical technique.Results：1. The effects of Saponins in Polygala on the vivo hippocampal long-term potentiation ofAlzheimer’s disease（AD） model rats：After the HFS 1 minute, 30 minutes, and 60 minutes,thefEPSP amplitude of the control group respectively reached 203.17±7.47%, 178.15±8.11% and164.17±7.03%, while the model group fEPSP amplitude was significantly lower than the controlgroup（ p<0.05）, only respectively reached 173.63±10.81%, 127.12±7.38% and 102.88±2.36%.The fEPSP amplitude of high dose Saponins in polygalae group respectively reached192.00±2.45%, 168.00±2.45% and 141.75±9.25%, which were higher （p<0.05） than the lowdose group’s 177.67±14.04%, 131.83±4.96% and 121.17±4.79%. Compared with the modelgroup both of high and low dose group’s fEPSP amplitude were obviously improved （p<0.05）.2. The effects of Saponins in Polygala on the hippocampal expression level of NR2A in ADmodel rats: The integral optical density values of control group, AD model group, low dosegroup and high dose group were respectly 30.12±3.45、11.74±1.69、20.78±2.66、25.86±2.98 .Compared with control group，the pyramidal cell layers in CA₁of AD models becameindiscriminate, sparse and the expression of NR2A in the AD modle group was obivously less（p<0.05）. Compared with model group, the expression of NR2A was significantly more in bothhigh dose group and low dose group（p<0.05, p<0.05）. Furthermore, the expression of NR2A wassignificantly more in high dose group than low dose group （p<0.05）.Conclusion: Saponins in polygala can significantly reduce the restraint to LTP induced byibotenic acid, and increase the expression of NR2A in the CA₁region of AD model rats, and improve the synaptic plasticity dose-dependently.