Objective: To study the effects of ethanol extracts from Portulacae Herba on learning and memory performances in senile mice induced by D-gal

and its mechanisms of effects. Method : The mice were randomly divided into 4 groups:control group

model group and the ethanol extracts from Portulacae Herba(1.0

0.5 g ·kg-1) groups. The control group was given sc of isotonic NaCl in the cervical back part while the other all were given sc D-gal(1 g ·kg-1)

once daily.The model was continuously established for 42 d

meanwhile medicine was given. Learning and memory performances were tested with step-through

water maze and Morris water maze test

and to determine the contents of malonaldehyde(MDA) and superoxide dismutase(SOD)

and to determine the activity of glutathione peroxidase(GSH-Px) in brain tissue simultaneously. Result : Compared with the model mice

the ethanol extract from Portulacae Herbacould significantly prolong the latency

and reduced the error frequency. It(1 g · kg-1) could obviously shorten escape latency and pass frequency of 1 min erect position in the senile mice. It could obviously reduce the content of MDA in the senile mice. Conclusion : The ethanol extract from Portulacae Herbacan improves the learning and memory performances of senile mice

the mechanism may be related to decrease in content of MDA in brain tissue.