Immediate epileptogenesis: Impact on brain in C57BL/6J mouse kainate model.

We have recently demonstrated immediate epileptogenesis in the C57BL/6J mouse, the strain that is resistant to kainate-induced neurotoxicity. By using a repeated low dose of kainate, we produced mild and severe status epilepticus (SE) models. In the present study, we demonstrate the impact of mild and severe SE, and spontaneous convulsive/nonconvulsive seizures (CS/NCS) on structure and function of the hippocampus, entorhinal cortex, and amygdala at 7, 14 and 28 day post-SE. Immunohistochemistry (IHC) of brain sections confirmed reactive astrogliosis and microgliosis, neurodegeneration, and increased neurogenesis in both groups. The epileptiform spike rate was higher in the severe group during first 12 days, but they decreased thereafter. Morris water maze test confirmed cognitive deficit in both mild and severe groups at 12d post-SE. However, MRI and IHC at 18 weeks did not reveal any changes in the hippocampus. These findings suggest that in C57BL/6J mice, immediate spontaneous CS could be responsible for early brain pathology or vice versa, however, the persistent spontaneous NCS for a long-term had no impact on the brain structure in both groups.