Objective  To explore the pathophysiological mechanism of subclinical seizures following hypoxic brain injury.   Methods  Totally 71 adult male SD rats were set in a close chamber with 8% nitrogen oxygen ventilation (0.5 L/min) till they lost breath every day for 7 d to induce hypoxic brain injury. Another 9 rats living in normal air condition served as control. Electroencephalography was carried out 20 min before the hypoxia and 2 h after hypoxic ventilation to detect subclinical seizures. The animals were sacrificed in 7

14

and 28 d after the end of hypoxia. Mossy fiber sprouting in the hippocampus were detected by Timm’s histochemical staining.   Results  Subclinical seizures occurred in 19.67% rats (14/71) following hypoxia. In Sub-clinical seizure group

brownish black granule sediment appeared in the pyramidal layer of CA3 region in 7 d following hypoxia

and became more intensive in bundle-like or patch-like way in 14 d

moreover

an obvious stained band was formed in 28 d. Compared with non-subclinical seizure group and control group

the scores of mossy fiber sprouting in the hippocampal CA3 region were higher in subclinical seizure group. But there was no significant difference of mossy fiber sprouting in dentate gyrus among the 3 groups above.   Conclusion Subclinical seizures may occur following hypoxia in adult rats

and prominent mossy fiber spouting is formed in the hippocampal CA3 region of these rats

which may be related to seizure following hypoxic brain damage .