Effects of Resuscitation at 100% Oxygen Environment or Room Air Environment on the Ultrastructure of Neurons in the Cerebral Cortex of Hypoxic Neonatal Rat / 中国实验动物学报

ABSTRACT

Objective To compare the effects of resuscitation at pure oxygen environment(100% oxygen) or room air environment (21% oxygen) on the uhrastructure of cerebral cortical neurons in hypoxic neonatal rat.Methods Twenty Sprague-Dawley neonatal rats aged 7 days were divided into the pure oxygen environment (POE) and room air environment groups (RAE) after hypoxia,and each group was divided again into 24 h and 72 h subgroups.The pups were placed in an incubator containing 8% O_2 to be at acute hypoxia continued for 2.5 h.The pups were reoxygenated immediately after the above mentioned hypoxia.The pups of POE group were then placed in an incubator containing 100% oxygen and the flow time was 30 rain.The pups of RAE group were reoxygenated with room air in an incubator for 30 rain.According to the planned time points the pups were sacrificed and the brain was removed at 24 h and 72 h after treatment,respectively.The tissue of frontoparietal cortex of the fight cerebral hemisphere was prepared for transmission electron microscopic examination.Results In each reoxygenation group,edema was found in the neurons,neuropil and intercellular space.In the RAE 24 h group,the nuclear membrane in neurons was unclear,the amount of cell organelles was reduced,the mitochondria were swollen with damages of cristae.The rough endoplasmic reticulum was dilatated or vaeuolized and with reduction of ribosomes.The Golgi complex was vacuolized.The number of lysosomes was obviously increased.In the RAE 72 h groups,the changes were similar to those of the former group,but apoptotic-like nuclei and necrotic neurons were more frequently seen. The cellular damages of POE 24 h group were milder than those of RAE 24 h group. The mitochondria and rough endoplasmie reticulum were more abundant and showed less pathological changes in the POE 72 h group as compared with those of RAE 72 h group. Conclusion The rats of POE reoxygenation display milder ultrastructural damages, less apoptosis, necrosis and edema in cerebral neurons than those in rats after RAE reoxygenation.The protective effect of POE resuscitation on cerebral damage of hypoxic neonate rats is superior to that after RAE resuscitation. This hypoxic neonatal rat model may serve as a suitable animal model for research on cerebral cortex neurons caused by hypoxia.