Abstract: AIMTo study the effects of puerarin on learning-memory behavior of aging mice induced by D-galactose and its possible mechanism of action. METHODSThe aging mice were induced by sc 0.12 g·kg^-1D-galactose for 6 weeks. The aging mice were treated with three doses of puerarin once a day for 5 weeks. The spontaneous behavior and the learning memory behavior were tested in the aging mice using open field and Y-maze at the next day after the last treatment. The structure of Gray I synaptic interface in the CA₃ area of the hippocampus was quantitatively analyzed by electronic microscope and computer image processing appliance. RESULTSCompared with the D-galactose control group, puerarin (60 mg·kg^-1) was shown to increase significantly the spontaneous behavior and explorative response in the open field, and improve remarkablely the learning and memory ability of the aging mice induced by D-galactose. Meanwhile, the thickness of post-synaptic density (PSD) was increased, and the width of the synaptic cleft in the hippocampus CA₃ area was shortened. CONCLUSIONPuerarin showed an improvement effect against the memory impairment in the modelling aging-mice induced by D-galactose. A pathological alteration of synaptic interface structure in hippocampus of the mice may be involved in the effect.