Epilepsy and synaptic reorganization in a perinatal rat model of hypoxia-ischemia

PURPOSE: One of the potential consequences of perinatal hypoxia-ischemia (H-I) is the development of epilepsy, and synaptic reorganization in the hippocampus has been associated with epilepsy after an injury. We tested the hypothesis that perinatal H-I will induce spontaneous motor seizures, hippocampal lesions, and synaptic reorganization in the dentate gyrus. METHODS: The right common carotid artery of 7-day-old rats was permanently ligated, and the rats were placed for 120 min into a chamber filled with 8% oxygen (37 degrees C). Animals were directly observed for chronic motor seizures for 7 to 24 months after the H-I insult. RESULTS: Nearly half of the rats (i.e., eight of 20) were seen to have spontaneous motor seizures after the H-I injury. The ipsilateral hippocampi from both the rats with seizures and the rats not seen to have seizures had hippocampal lesions and increased amounts of Timm stain in the inner molecular layer (IML) compared with controls. The contralateral hippocampi from the rats with seizures, but not the hippocampi from the rats not seen to have seizures, had significantly increased amounts of Timm stain in the IML. CONCLUSIONS: These results suggest that perinatal H-I can induce epilepsy, ipsilateral hippocampal lesions, and mossy fiber sprouting in the lesioned and contralateral hippocampus.