Objective      To observe the dynamic changes of apoptosis in rat cerebral cortex neurons after hypoxia.       Methods      Rat cerebral cortex neurons were primarily cultured from SD rats born within 24 h and then identified by immunocytochemical assay. Then the identified cells were cultured in the medium containing 100 μmol/L CoCl

2

to simulate hypoxic condition. The cells cultivated in normal condition served as normal control (normoxia group). Ultrastructural changes of the neurons were observed by transmission electron microscopy (TEM). Neuronal apoptosis were observed by TUNEL assay.       Results      TEM displayed that the morphology of neurons was normal

so was the structure of chromatin

endopl

asmic reticulum and mitochondria in normoxia group

while

cellular edema

organelle damage or disappearance were seen in the hypoxia group. TUNEL showed that obvious apoptosis were found in hypoxic cells

with significant difference with normoxia group (P0.01). The apoptosis reached its peak in 48 h after hypoxia (0.187±0.007)

significantly higher than those in 12

24 and 72 h (P0.01).       Conclusion      Apoptosis is a dynamic process in hypoxic-ischemic brain injury

and an important pattern of neuronal death. Intervention for neuronal apoptosis should be performed in an appropriate time window to effectively treat hypoxic-ischemic encephalopathy.