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BACKGROUND: Aquaporin-4 (AQP-4) is closely related to the formation of brain edema. Neuronal apoptosis plays an important part in the conversion of swelled neuron following traumatic brain injury. At present, the studies on the protective effect of ketamine on brain have involved in its effect on aquaporin-4 expression and neuronal apoptosis in the brain tissues following brain injury in rats.OBJECTIVE: To observe the effect of ketamine on AQP-4 expression and neuronal apoptosis in the brain tissue following rat brain injury, and analyze the time-dependence of ketamine in the treatment of brain injury.DESIGN: Randomized grouping design, controlled animal trial.SETTING: Department of Anesthesiology, the Medical School Hospital of Qingdao University.MATERIALS: Totally 150 rats of clean grade, aged 3 months, were involved and randomized into control group and ketamine-treated group, with 75 rats in each. Each group was divided into 5 subgroups separately at 6,12, 24, 48 and 72 hours after injury, with 15 rats at each time point. Main instruments and reagents:homemade beat machine, ketamine hydrochloride (Hengrui Pharmaceutical Factory, Jiangsu), rabbit anti-rat AQP-4 polyclonal antibody, SABC immunohistochemical reagent kit and TUNEL reagent kit (Boster Co.,Ltd.,Wuhan).METHODS: This trial was carried out in the Institute of Cerebrovascular Disease, Medical College of Qingdao University during March 2005 to February 2006. A weight-dropping rat model of brain injury was created with Feeney method. The rats in the ketamine-treated group were intraperitoneally administered with 50 g/L ketamine (120 mg/kg) one hour after injury, but ketamine was replaced by normal saline in the control group. In each subgroup, the water content of cerebral hemisphere was measured in 5 rats chosen randomly. The left 10 rats in each subgroup were transcardiacally perfused with ketamine, then the brain tissue was made into paraffin sections and stained by haematoxylin and eosin. Neuronal morphology was observed. AQP-4 expression and neuronal apoptosis were measured with immunohistochemical method and TUNEL method respectively.MATN OUTCOME MEASURES: Water content in brain tissue, neuronal morphology, the number of AQP-4positive neurons and TUNEL positive neurons in rats of two groups at each time point after injury.RESULTS: Totally 150 rats entered the stage of result analysis. ① Water content of brain tissue: The water content of brain tissue at each time point after injury in the ketamine-treated group was lower than that in the control group. There were very significant differences in water content at 12 and 24 hours after injury respectively between ketamine-treated group and control group [(77.34±2.35)% vs. (82.31 ±1.48)%;(78.01 ±2.21 ) ％ vs. (83.86±2.37)％,t=4.001 6,4.036 7, both P ＜ 0.01]. ② Neuronal morphology: Pathological changes in traumatic region and peripheral region of injury in the ketamine-treated group were significantly lessened, and necrotic and apoptotic cells in the ketamine-treated group were also significantly reduced as compared with control group. ③ AQP-4 expression: AQP-4 positive neurons at each time point in rnthe ketamine-treated group were significantly less than those in the control group. There were very significant differences in AQP-4 expression at 12 and 24 hours after injury between ketamine-treated group and control group [(34.17±4.74) /visual field vs. (43.42±5.65) /visual field;(40.83±3.17) /visual field vs.(58.88±6.23) /visual field,t=3.966 3,8.165 7, both P＜ 0.01]. ④ Neuronal apoptosis: TUNEL positive neurons at each time point in the ketamine-treated group were less than those in the control group. There were very significant differences in the neuronal apoptosis at 12 and 24 hours after injury between ketamine-treated group and control group [(26.25±3.04) /visual field vs. (32.75±4.39) /visual field; (29.33±4.02) /visual field vs. (39.83±5.61) /visual field,t=3.849 3,5.169 2, both P ＜ 0.01].CONCLUSION: Ketamine can reduce brain edema, AQP-4 expression and neuronal apoptosis following brain injury in rats, and has obvious therapeutic effect on brain injury, especially at 12 and 24 hours after injury.