Hippocampal Nogo-A and neo-Timm's staining in amygdala kindling rats.

PURPOSE

Nogo-A, one of the axon regeneration inhibitors, has been shown to be up-regulated in both the experimental and human temporal lobe epilepsy. However, the role of Nogo-A in mossy fiber sprouting (MFS) relative to epileptogenesis is unknown. This work was designed to examine the relationship of the hippocampal Nogo-A protein expression with MFS during the development of amygdala kindling.

METHODS

Using immunohistochemistry and neo-Timm's histological procedures, we evaluated the distribution and density of Nogo-A and Nogo-66 receptor (Ng-R) expression and MFS in the bilateral hippocampus of amygdala kindling rats.

RESULTS

Nogo-A expression in the ipsilateral hippocampus gradually increased with the development of kindling in the sector CA2-3. In contrast, no increased Nogo-A expression was observed in the contralateral hippocampus as the rats advanced to stage 5 kindled seizures. Furthermore, poorer Nogo-A and Nogo-66 receptor (Ng-R) expression were observed in the dentate granule cells as aberrant MFS occurred.

CONCLUSIONS

In amygdala kindling rats, generalized stage 5 seizures were not associated with increased Nogo-A expression in the contralateral hippocampus supporting the concept that seizures by themselves do not induce Nogo-A expression. Furthermore, in the ipsilateral hippocampus, the expression of Nogo-A relative to MSF suggests that this protein may partially control aberrant synaptic reorganization during epileptogenesis.