Ultrastructural features of astrocytes in the cortex of the hippocampal gyrus and in the neocortex of the temporal lobe in an experimental model of febrile seizures and with the use of topiramate

The objective of the current study was ultrastructural assessment of astroglia in specimens of the hippocampal cortex and neocortex of the temporal lobe in our own experimental model of febrile seizures (FS) in rats, as well as the analysis of the influence of a structurally novel broad spectrum anticonvulsant, topiramate (TPM), upon these cells in the CNS regions studied. The current study was inspired by some interesting literature reports on the in vitro investigation into the biological effects of TPM in primary cultures of rat cortical astrocytes and by the lack of data concerning astroglial morphology in vivo in an experimental model with this antiepileptic. In the FS group, the most pronounced changes in the study cell population referred to protoplasmic astroglia and were observed in approximately 3/4 of these cells. The abnormalities were similarly expressed in the two CNS regions studied, in terms of both quantity and quality. They were characterized by considerable swelling and degenerative changes, both in astrocytic perikarya and their processes. Changes were visible in the elements of the granular endoplasmic reticulum and mitochondria, which had a condensed configuration. In the group receiving topiramate directly after the induction of FS, submicroscopic changes in protoplasmic astrocytes were similarly expressed as in the FS group. However, in the group receiving the drug prior to the induction of FS its protective action was observed on the morphology of approximately 1/3 of the population of the protoplasmic astroglial cells. The remaining protoplasmic astrocytes still showed features of considerable or moderately pronounced injury. The beneficial effect of TPM on the ultrastructure of part of the population of the protoplasmic astroglia in the group in which the drug was applied prior to the induction of FS can be explained, among others, by a protective effect of the blood-brain barrier enhanced by the drug administration, as indicated by our earlier findings.