BACKGROUND: Hypothermia plays a protective role in cerebral ischemia/reperfusion injury. Dose combination with batroxobin, an active drug for treating cerebrovascular disease, will enhance its protection? OBJECTIVE: To explore the effects of hypothermia, batroxobin, hypothermia combined with batroxobin on complete cerebral ischemia/reperfusion injury in gerbils.DESIGN: A randomized block comparison observation. SETTING: Jiangsu Key Lab of Anesthesiology. MATERIALS: Experimental animal: Sixty Mongolia gerbils weighing 50-80 g, male or female, were provided by the Animals Center of Xuzhou Medical College. Drugs and agents: Batroxobin was provided by Dongling Phar maceutical Industry Organization (Japan). Superoxide dismutase (SOD) and malondiadehyde (MDA) kits were offered by Nanjing Jiancheng Bioengineering Institute. Other reagents were all import or national analytical pure grade. HITACHI R22A refrigerated high-speed centrifuge, and HARRIS ultra-hypothermia refrigerator were used.METHODS: The experiments were completed in Jiangsu Key Lab of Anesthesiology from May 2004 to January 2005. ① The animals were divided into 6 groups by random member table method: sham-operated group (n =6), ischemia control group (n =6), normothermia group (n =12), hypothermia group (n =12), batroxobin group (n =12) and hypothermia+batroxobin group (n =12). Gerbil rats were abdominally anesthetized with sodium pentobarbital. The neck skin was incised to separate bilateral common carotid arteries. Complete cerebral ischemia models were established by occluding bilateral common carotid arteries with artery clamp for 10 minutes, then the clamp was loosened to perfuse the arteries. Iso-electric level of brain electric wave showed the models were established successfully. The gerbils in the batroxobin group and hypothermia+batroxobin group were abdominally injected with batroxobin (8 BU/kg) while reperfusion, and isovolumetric saline was administered to the gerbils in the other groups without drugs. The animals in the sham-operated group were anesthetized at normal temperature (36 ℃) and the above mentioned procedures were performed except for the bilateral common carotid artery occlusion. The animals were decapitated and the brains were taken out after the operation immediately. The controls were occluded for 10 minutes, and then extracted the brains. In each group, animals were kept in boxes with lamps to maintain the temperature. Animals in the hypothermia group were laid in the appliance plate and covered with ice-bag to keep hypothermia, drum membrane temperature decreased to (32±0.5) ℃ within about 5 minutes and then kept for 20 minutes and 60 minutes; while in the normothermia group, it was kept stable at (36±0.5) ℃, then the brains were harvested at 20 and 60 minutes of reperfusion after ischemia. The temperature was monitored continuously by thermistor. ② Except the sham-operated group and ischemia control group, 6 gerbils respectively were selected from the other groups to remove bilateral hippocampi, then SOD activity and the MDA content were detected at 20 minutes and 60 minutes after reperfusion. ③ The differences of the measurement data were compared using the t test. MAIN OUTCOME MEASURES: Changes of SOD activity and MDA content in the bilateral hippocampi at 20 minutes and 60 minutes after reperfusion respectively.RESULTS: All the 60 gerbils were involved in the analysis of results. ① Changes of SOD activity: The SOD activities in the normothermia group, batroxobin group and hypothermia+batroxobin group at 20 minutes [(396± 41 ), (447±53), (491 ±25) kNU/L] were lower than that in the ischemia control group [(547±35) kNU/L, P ＜ 0.05]. The SOD activities at 60 minutes in the hypothermia group, batroxobin group, and hypothermia+batroxobin group [(502±34), (519±49), (597±48) kNU/L] were obviously lower than that in the normothermia group (P ＜ 0.01). ② Changes of MDA content: The MDA contents in normothermia group and hypothermia+batroxobin group at 60 minutes [(1292±274), (763±108) μmol/L] were obviously higher than that in the ischemia control group [(907±148) μmol/L, P ＜ 0.01]. The MDA contents in the hypothermia group at 60 minutes, batroxobin group at 20 and 60 minutes and hypothermia+batroxobin group at 60 minutes [(827±102), (1 092±127), (818± 105), (763±108) μmol/L] were lower than that in the normothermia group (P＜ 0.05). CONCLUSION: The SOD activity showed a descending tendency as the time of ischemia prolonged under normalthermia, and the SOD activities were increased in the hypothermia group and batroxobin group, and the combination of hypothermia and batroxobin had better effect than the single application. The MDA content showed an ascending tendency as the time of reperfusion prolonged under normalthermia, both hypothermia and batroxobin can decrease the MDA content, and the combination of them had much better effect. Both hypothermia and batroxobin have the protective effects on brain, and the combination of them can enhance the brain protection.