AIM To explore the effects of Kaixin Powder (Polygalae Radix,Ginseng Radix et Rhizoma,Poria and Acori tatarinowii Rhizoma) on hippocampal long-term potentiation (LTP) in vivo in APP/PS1 transgenic mice and expression of PSD-95 in hippocampus CA1 area and cerebral cortex.METHODS Thirty-two 3-monthold male APP/PS1 mice were randomly divided into model group,Donepezil [0.75 mg/(kg · d)] group,Kaixin Powder [1.5,3 g/(kg · d)] groups.C57/BL6 mice were used as the control group.Kaixin Powder and Donepezil were administered to the APP/PS1 mice for three months,respectively.Afterwards,the LTP in vivo was recorded in a perforant pathway-dentate gyrus in the hippocampus.Immunohistochemical method was used for measuring the expression of PSD-95 in hippocampus CA1 area and cerebral cortex.RESULTS The fEPSPs slopes were significantly decreased in the model group as compared with the control group.Kaixin Powder or Donepezil treatment significantly enhanced the fEPSPs slopes in the model group.The average optical density of PSD-95 positive cells in hippocampus CA1 area and cerebral cortex was obviously decreased in the model group.Donepezil increased the average optical density of PSD-95 positive cells in hippocampus CA1 area.Kaixin Powder [1.5 g/(kg · d)] increased the average optical density of PSD-95 positive cells in hippocampus CA1 area and cerebral cortex.Kaixin Powder [3 g/(kg · d)] increased the average optical density of PSD-95 positive cells in cerebral cortex.CONCLUSION Kaixin Powder can promote the LTP formation in APP/PS1 transgenic mice and enhance synaptic plasticity,which may be related to the regulation of protein expression of PSD-95.