Relationships between astrocytes and absence epilepsy in rat: An experimental study

Astrocytes take part in the modulation of neuronal activity through the uptake and release of both GABA and glutamate. In the present study we aimed to quantify the number of astrocytes expressing the astrocyte marker glial fibrillary acidic protein (GFAP) in the somatosensory cortex (SSCx), ventrobasal (VB), centromedial (CM), reticular (TRN) and dorsal lateral geniculate (dLGN) nuclei of thalamus in Genetic Absence Epilepsy Rats from Strasbourg (GAERS), Wistar Albino Glaxo Rats from Rijswijk (WAG/Rij) and control Wistar animals. Further, we aimed to compare the GFAP protein expression levels between the three animal strains. The GFAP-immunohistochemistry was applied to sections from the SSCx, VB, CM, TRN and dLGN and GFAP-positive astrocytes were quantified for the three animal strains. Further, GFAP Western Blot was applied to the tissue samples from the same regions of the three strain. The data obtained from Wistar animals were compared with GAERS and WAG/Rij animals. The number of GFAP-positive astrocytes per unit area in all brain regions studied showed high significance between Wistar-GAERS and Wistar-WAG/Rij except the dLGN. The GAERS had significant higher endogenous GFAP expression in all brain regions studied compared to Wistar and WAG/Rij animals. These findings demonstrate a discrete difference in both GFAP-positive astrocyte populations and GFAP protein expression levels between Wistar and genetically epileptic strains (GAERS and WAG/Rij). Absence seizures are thought to result from a possible imbalance in glutamatergic and GABAergic neurotransmission. Astrocytes regulate the concentration of glutamate and GABA in the extracellular space in the brain, the difference in the astrocyte population and GFAP protein expression in the epileptic strains clearly shows the involvement of astrocytes in the mechanism of absence epilepsy.