Objective         To determine the effects of emodin on the protection of learning and memory abilities and on SOD activity and MDA content in the brain tissue of rats after hypoxic brain injury induced by hypobaric hypoxia environment.         Methods        A total of 80 male Wistar rats were randomly divided into control group (n=16)

hypoxia group (n=16) and emodin intervention group (n=48). Hypoxia environment cabin was used to contain the rats of the 2 latter groups and force them to swim 50 min every 3 h for consecutive 24 hours. The rats of control group were feed in normal condition. The latter group was further assigned into 3 subgroups according to different doses of emodin [15

30 and 60 mg/(kg·d)

n=16]

and was perfused with corresponding doses intragastrically for 3 consecutive days before entering the hypoxia cabin

while the rats of the other 2 groups were given with same volume of normal saline (1 mL). Morris water maze automatic image acquisition and processing system was used to find the mean escape latency (MEL) for  hidden platform. Brain water content was measured by wet to dry mass ratio method. SOD activity and MDA content in the cerebral tissue were detected.         Results        In the Morris water maze test

MEL was significantly longer in the hypoxia group than the control (P0.01)

and was obviously shorter in the emodin intervention groups  than the hypoxia group (P0.05

P0.01); Brain water content was significantly increased in the hypoxia than the control (P0.01)

but the emodin intervention group had lower water content than the hypoxia group (P0.05

P0.01) in a dose-dependent manner.  In the determination of the activity of brain tissue SOD and the content of MDA

the activity of SOD was significantly lower (P0.01) while MDA content was increased (P0.01) in hypoxia group than the control. Emodin treatment resulted in increased SOD activity (P0.05

P0.01) and decreased MDA content (P0.05

P0.01) than in the hypoxia group.         Conclusion        Emodin can increase the activity of SOD in brain tissue of rats

decrease the content of MDA

and improve the ability of learning and memory in rats.