RESUMO
OBJECTIV E To investigate the effect s and mechanism of the ethanol extract of Tiarella polyphylla （“TPE”）on learning and memory impairment in mice. METHODS Male Kunming mice were randomly divided into normal group ，model group，positive group （donepezil hydrochloride 4 mg/kg）and TPE low-dose ，medium-dose and high-dose groups （150，300，600 mg/kg），with 10 mice in each group. Drug administration groups were given relevant medicine intragastrically once a day ，and normal group and model group were given water intragastrically once a day ，for consecutive 22 d. On the 17th day ，administration groups and model group were intraperitoneally injected with scopolamine hydrobromide （3 mg/kg）to establish a model of learning and memory impairment. The learning and memory ability of the mice were evaluated by the Morris water maze. Hematoxylin-eosin （HE） staining was used for morphological observation of hippocampus cells of the mice. The levels of acetylcholinesterase （AChE），choline acetyltransferase （ChAT），superoxide dismutase （SOD），malondialdehyde（MDA），interleukin-6（IL-6）and tumor necrosis factor-α（TNF-α）in cerebral tissue as well as the relative expression of phosphorylated Tau protein （p-Tau），β-site amyloid precursor protein cleaving enzyme 1（BACE1）and amyloid precursor protein （APP）in hippocampus tissue were all detected. RESULTS The escape latency of mice in positive group ，TPE medium-dose and high-dose groups were all significantly shortened than the model group on the 4th to 5th day of training ，while the times of crossing platform and the percentage of movement distance in target quadrant were significantly increased （P＜0.05）. Compared with model group ，the neurons in the hippocampal CA 1 region of mice were increased to var ying degrees in administration groups ，the ne urons in solidified and atrophic state decreased ，and the arrangement of neurons tended to be close；the levels of ChAT and SOD in cerebral tissue were significantly increased in positive group and TPE medium-dose and high-dose groups ；the levels of AChE ，MDA，IL-6，the levels of TNF-α and relative expression of p-Tau ，BACE1 and APP in hippocampus tissue were decreased significantly （P＜ 0.05）. CONCLUSIONS TPE can improve the learning and memory impairment induced by scopolamine in mice ，and the mechanism may be related to balancing the brain cholinergic system ，alleviating oxidative stress injury ，improving inflammatory response，and inhibiting the overexpression of p-Tau ，BACE1 and APP .