Objective     To study the pathologic changes of hippocampus during the model development and explore the mechanism of epileptogenesis by observing the morphologic changes of hippocampal formation in rat of kainate-induced chronic temporal lobe epilepsy (TLE).       Methods     Thirty Wistar rats were injected of Kainic acid at dose of 2 μg/20 μl into the lateral cerebral ventricle under the guidence of stereotactic technique to make a epileptic focus

and subgrouped under acute phase

silent period and chronic phase. Another 10 rats received normal saline as controls. The rats were killed at 1 day

15 day and 6 months after epileptic model establishment

and the hippocampus was taken out for HE staining

TUNEL staining

Timm’s staining

NSE staining.      Results     By cell counting

the neuron loss mainly occurred in acute phase

worst in CA3 and CA4

moderate in CA1 and CA2

and no loss in the dentate gyrus. The cell apoptosis in hippocampal structure was detected by TUNEL staining. Timm’s staining showed that mossy fiber began sprouting in silent period and increased continuously.      Conclusion     The morphologic changes of hippocampal formation in rat of kainate-induced TLE is mainly the neuron loss and the glia hyperplasy.