Abstract: Objective To investigate the change of myelin in the brain of rats after hypoxia.Methods Three-day old neonatal rats were randomly divided into control group and hypoxia group.No treatment was applied to control group.But the hypoxia group was put to a closed vessel and mixed gas with 8% O₂ and 92% N₂ were filled into the vessel for 90 minutes.Twenty-eight days after the animal model was built,cerebral cortex,hippocampus and lateral ventricle were obtained from both groups.Then the tissue specimens were observed under the electron microscope and a quantitative analysis on the myelin was conducted.Results The results of electron microscopy indicated that compared to control group,cerebral cortex,hippocampus and lateral ventricle of hypoxia group appeared to have the neuron nuclear fragmentation and karyopyknosis.Statistical analysis suggested that the number and ratio of myelinated axons significantly decreased in hypoxia group compared to control group(P=0.000 in cerebral cortex,P=0.009 in hippocampus and P=0.000 in lateral ventricle,respectively).Conclusion Hypoxia alone can cause the pathological changes of demyelination in the hypoxia-ischemia brain injury model.

Key words: hypoxia, model, myelinated axon