Abstracts

The contribution of hippocampal damage to the generation of chronic spontaneous seizures is under dispute. The aim of the study was to address this controversial question by examining whether the severity of neuronal loss and density of mossy fiber sprouting correlate with the seizure frequency in epilepsy induced by traumatic brain injury (TBI). The recently developed rat model for post-traumatic epilepsy was used in the study. Epileptogenesis was induced in 18 rats by lateral fluid percussion injury (FPI). After FPI long term video-electroencephalographic monitoring was performed for 10 months to prove development of post-traumatic epilepsy and follow seizure frequency. The density of mossy fiber sprouting was analysed from Timm-stained sections. The loss of hippocampal neurons was assessed from thionin-stained sections. In the overall group of 18 traumatized animals the correlation was found between density of mossy fiber sprouting and hilar cell loss in hippocampus ipsilateral to trauma (p[lt]0.01). In the group of epileptic animals (9 out of 18) there was no correlation between density of mossy fiber sprouting and hilar cell loss. Further, no correlation between seizure frequency and density of mossy fiber sprouting or seizure frequency and hilar cell loss was found in the epileptic group. In contrast to that, there was a clear correlation between seizure frequency and overall hippocampal damage (dentate gyrus+CA3+CA1) both ipsilaterally (p[lt]0.05) and contralaterally (p[lt]0.05). Our data indicate that the overall neuronal damage in the hippocampus after fluid percussion injury in rat can contribute to the occurance of chronic spontaneous seizures and the severity of post-traumatic epilepsy. (Supported by Academy of Finland, CIMO, EUCARE, Sigrid Juselius Foundation)