BACKGROUND: Push-pull effect is often caused during maneuver, and the changes of unconsciousness induced can affect or damage cerebral neurons at various degrees. OBJECTIVE: To observe the effect of simulated push-pull maneuver at various degrees on injury of hippocampal neurons in rats and analyze its phase effect. DESIGN: Randomized control study. SETTING: Physiological Department of Jilin Medical College. MATERIALS: A total of 40 healthy male Wistar rats, of clean grade, weighting 205-300 g, aged 3-4 months, were randomly divided into control group (n=4) and three push-pull experimental groups, including ±2 Gz group (intensity: -2 Gz to +2 Gz, n=12), ±6 Gz group (-6 Gz to +6 Gz, n=12) and ±8 Gz group (-8 Gz to +8 Gz, n=12). METHODS: The experiment was completed in the Physiological Department of Jilin Military Medical College from March 2002 to May 2003. ① Rats in the experimental groups were put at the specially rolling arm of animal centrifugal machine. Then, they were pushed and pulled with ±2 Gz, ± 6 Gz and ±8 Gz, respectively. The jolt was 1 Gz/s. However, rats in control group were not treated with any ways. ② Stroke index and neurological evaluation were performed on rats in the experimental groups at 0.5, 6 and 24 hours after push-pull. Stroke index was 25 points in total. The higher the scores were, the severer the cerebral injury was. Neurological evaluation was 10 points in total. The higher the scores were, the severer the nerve injury was. ③ Hippocampal tissue in brain of rats were selected to cut into sections at each time points, and form and distribution of neurons were observed in hippocampal areas with HE staining. Degrees of neuronal injury in hippocampal CA1 area were assayed after push-pull at various degrees with electron microscope. ④ Measurement data were compared with t test. MAIN OUTCOME MEASURES: ① Stroke index and neurological evaluation; ② Form and distribution of neurons in hippocampal areas; ③ Degrees of neuronal injury in hippocampal CA1 area. RESULTS: A total of 40 rats were involved in the final analysis. ① Stroke index and neurological evaluation of rats in experimental groups: At 30 minutes and 6 hours after push-pull exposure, stroke index and neurological evaluation were higher in ±6Gz group and ±8 Gz group than those in control group (P < 0.01), especially at 6 hours after push-pull exposure, those in ±8 Gz group were the highest at each time points [(11.00±2.16), (5.75±1.70) points]. At 24 hours after exposure, those were decreased as compared with those within the former two time points, but the values were still higher than those in control group (P < 0.05-0.01). ② Results of HE staining: At 6 and 24 hours after exposure, partially neuronal degeneration was observed in pyramidal layer in ±6 Gz group and ±8 Gz group, including crenation of neurons, triangle or polygon, and karyopycnosis, especially the injury in ±8 Gz group was the most obvious at 6 hours after exposure. ③ Results of ultrastructure with electron microscope: Partially neuronal degeneration at various degrees was observed in hippocampal CA1 area in ±2 Gz group at 6 hours after exposure and in ±6 Gz group and ±8 Gz group at 6 and 24 hours after exposure. At 6 hours after exposure, nucleus of hippocampal neurons in ±8 Gz group was irregular and umbilication. Caryotin was aggregated, nuclear matrix was swelled and disorder, and vacuolation was also observed. Rough endoplasmic reticulum was expanded, mitochondrium was swelled, and crista was disappeared. CONCLUSION: ① Push-pull cannot damage hippocampal neurons of rats in ±2 Gz group. ② Exposure can cause injury of hippocampal neurons of rats in ±6 Gz group and ±8 Gz group, especially the injury is the severest at 6 hours after exposure in ±8 Gz group and relieves gradually 24 hours later. BACKGROUND: Push-pull effect is often caused during maneuver, and the changes of unconsciousness induced can affect or damage cerebral neurons at various degrees. OBJECTIVE: To observe the effect of simulated push-pull maneuver at various degrees on injury of hippocampal neurons in rats MATERIALS: A total of 40 healthy male Wistar rats, of clean grade, weighting 205-300 g, aged 3-4 months, were randomly selected divided into control group (n = 4) and three push-pull experimental groups, including ± 2 Gz group (intensity: -2 Gz to +2 Gz, n = 12), ± 6 Gz group (-6 Gz to +6 Gz , n = 12) and ± 8 Gz group (-8 Gz to +8 Gz, n = 12). METHODS: The experiment was completed in the Physiological Department of Jilin Military Medical College from March 2002 to May 2003. ① Rats in the experimental groups were put at the specially rolling arm of animal centrifugal machine. Then, they were pushed However, rats in control group were not treated with any ways. ② Stroke index and neurological evaluation were performed on rats in the experimental groups at 0.5, 6 and 24 hours after push-pull. S higher levy were 25 points in total. The higher the scores were, the severer the cerebral injury was. Neurological evaluation was 10 points in total. The higher the scores were, the severer the nerve injury was. ③ Hippocampal tissue in brain of rats were selected to cut into sections at each time points, and form and distribution of neurons were observed in hippocampal areas with HE staining. Degrees of neuronal injury in hippocampal CA1 area were assayed after ④ Measurement data were compared with t test. MAIN OUTCOME MEASURES: ① Stroke index and neurological evaluation; ② Form and distribution of neurons in hippocampal areas; ③ Degrees of neuronal injury in hippocampal CA1 area. RESULTS: A total of 40 rats were involved in the final analysis. ① Stroke index and neurological evaluation of rats in experimental groups: At 30 minutes and 6 hours after push-pull exposure, stroke index and neurological evaluation were higher in ± 6 Gz group and ± 8 Gz group than those in control group (P <0.01), especially at 6 hours after push-pull exposure, those in ± 8 Gz groups were the highest at each time points [(11.00 ± 2.16), ( 5.75 ± 1.70) points]. At 24 hours after exposure, those were decreased as compared with those within the former two time points, but the values ​​were still higher than those in control group (P <0.05-0.01). ② Results of HE staining: At 6 and 24 hours after exposure, partially neuronal degeneration was observed in pyramidal layer in ± 6 Gz group and ± 8 Gz group, including crenation of neurons, triangle or polygon, and karyopycnosis, especially the injury in ± 8 Gz group was the most obvious at 6 hours after exposure. ③ Results of ultra structure with electron microscope: Partially neuronal degeneration at various degrees was observed in hippocampal CA1 area in ± 2 Gz group at 6 hours after exposure and in ± 6 Gz group and ± 8 Gz group at 6 and 24 hours after exposure. At 6 hours after exposure, nucleus of hippocampal neurons in ± 8 Gz group was irregular and umbilication. Caryotin was aggregated, nuclear matrix was swelled and disorder, and vacuolation was also observed. Rough endoplasmic reticulum was expanded, mitochondrium was swelled, and crista was disappeared. CONCLUSION: ① Push-pull can not damage hippocampal neurons of rats in ± 2 Gz group. ② Exposure can cause injury of hippocampal neurons of rats in ± 6 Gz group and ± 8 Gz group, especially the injury is severely at 6 hours after exposure in ± 8 Gz group and relieves gradually 24 hours later.