Abstract: Objective To investigate the effect and mechnism of lentinan (LNT) on learning and memory abilities in rats with Alzheimer's disease (AD).Methods Ten rats were selected randomly as normal control group (normal saline) from 50 healthy Sprague-Dawley (SD) rats;the other 40 rats were assigned into AD model group,from which 30 model rats were randomly selected and divided into three groups:a model group (normal saline),high dose LNT intervention group (LNT-H,50 mg/kg) and low LNT dose intervention group (LNT-L,10 mg/kg).Then Morris water maze was used to test learning and memory abilities.Reagent-boxes were used to observe the activity of superoxide dismutase (SOD) and catalase (CAT) and content of monoamine oxidase (MAO) in cerebral cortex.c-fos expression level in hippocampus was observed by immunofluorescence assay.Results Compared with that of the control group,the escape latency (63.67±5.19 seconds) at the 5th day of the model group was significantly increased (P<0.01),while the times of crossing platform (2.09±1.22) were obviously decreased (P<0.01);in addition,for the rats of the model group,the activity of CAT (4.98±1.32) and SOD (9.39±2.52) in hippocampus were obviously decreased (P<0.01),the MAO content (68.62±9.67 nmol/100 mg pro)increased (P<0.01),and the expression of c-fos in hippocampal tissue was significantly increased (P<0.01).In contrast with the model group,the escape latency (35.67±4.68 s) at the 5th day was obviously shortened (P<0.01),while the times of crossing platform (4.89±1.01) were obviously increased in the LNT-H group (P<0.01);in cerebral cortex,the activity of CAT (7.18±1.19) and SOD (13.45±2.21) were obviously increased (P<0.01) but the MAO content (38.33±6.53 nmol/100 mgpro) markedly decreased (P<0.01);the expression of c-fos in hippocampal tissue was significantly reduced (P<0.01).Conclusion Lentinan may improve learning and memory ability through enhancing antioxidant capacity of rat brain and regulating the expression of hippocampus c-fos protein in AD rats.