Neuropilin-2 is overexpressed in the rat brain after limbic seizures

Structural rearrangement and synaptic reorganization are known to occur in the brain after seizures. If neuronal rearrangement after seizures always results in abnormal hyperexcitability, it would provide an accurate pathway to the appropriate target and as a result, it may be the mechanism of epileptogenesis. This study examined the mechanism of axon guidance in the mature rat brain after seizures by evaluating the expression of the axonal guidance molecule, neuropilin-2. We assessed the expression of neuropilin-2 by northern blotting and immunohistochemistry in rat with seizures created by kindling stimulation and kainate injection.The neuropilin-2 mRNA level was increased in the whole brain of the rats at 24 h after either type of seizure. Neuropilin-2 mRNA was not increased at 2 weeks after the last stimulation. Immunohistochemistry demonstrated that neuropilin-2 protein was increased in the dentate gyrus and the entorhinal cortex in the both seizure models. These findings suggested that there was overexpression of neuropilin-2 in the brains of mature rats with different types of seizure. Accordingly, neuropilin-2 might regulate remodeling after seizures as it does during the development of the hippocampal formation. Our findings suggest that axons may not project and outgrow 'aberrantly' after seizures, but may be regulated by the chemorepellent effect through neuropilin-2.