低+Gz重复暴露后对高+Gz致大鼠脑损伤的影响

目的：探讨低 Gz重复暴露后对高 Gz致脑损伤的影响。方法：SD大鼠40只,随机分为正常对照组（5只）, 10Gz/5min单次暴露组（5只）和 4Gz/3min暴露1次、3次和5次组（每组10只,每天暴露1次）,分别于暴露后1d和6d再暴露于 10Gz/5min,于 10Gz暴露后3d处死取脑,观察脑组织病理损伤情况。结果： 4Gz/3min锻炼1-5次,每天1次,大鼠脑组织未见病理性损伤。而 10Gz/5min单次暴露后,在皮层、海马、丘脑等部位均可见到变性的神经元,个别脑区出现神经细胞凝固性坏死。经过 4Gz/3min锻炼3次和5次后再暴露于 10Gz,变性神经元的数目在顶叶皮层、梨状皮层、海马和丘脑下部等部位明显减少。结论： 4Gz/3min反复锻炼3次和5次,再暴露于损伤强度的 10Gz/5min,其神经元损伤程度明显轻于 10Gz/5min单次暴露。 Gz作用下在脑部同样存在缺血耐受现象。

Influences of Repeated Lower +Gz Exposures on High +Gz Exposure Induced Brain Injury in Rats

Objective. To explore the influence of repeated lower +Gz exposures on high +Gz exposure induced brain injury in rats. Method. Forty SD male rats were randomly divided into control group (5 rats), +10 Gz/5 min group (5 rats) +4 Gz exposure one time, three times and five times group (10 rats each group). After 1 d or 6 d of +4 Gz exposure each group were exposed to +10 Gz again. Three days after +10 Gz exposure the neuron damage was observed by light microscope in HE stained section. Result. There was no brain damage after repeated +4 Gz/3 min exposure 5 times so it was reasonable to use this exposure intensity as ischemia stimulation. +10 Gz/5 min exposure could result in irreversible neuron damage such as neuron degeneration and coagulation necrosis. The experiment results suggested that after +10 Gz/5 min exposure there were degenerated neurons in cortex, hippocampus and thalamus. The number of degenerated neurons were obviously decreased in cortex, hippocampus and thalamus when exposed to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. Conclusion. The degree of neuron damage was obviously slight at the time of exposure to +10 Gz/5 min again after repeated +4 Gz/3 min 3-5 times. The ischemia tolerance at the time of exposure to +Gz was similar to other brain ischemia.