Specific alteration in the expression of glial fibrillary acidic protein, glutamate dehydrogenase, and glutamine synthetase in rats with genetic absence epilepsy

Astrocytes play a predominant role in energy metabolism and in the cataboli sm of gamma-aminobutyric acid (GABA) and glutamate, neurotransmitters criti cally involved in epileptic processes. We show specific astrocytic alterati ons in the genetic absence epilepsy rats from Strasbourg (GAERS). Spontaneo us absence seizures appear in this strain in the cortex and thalamus after the age of 1 month. In these brain structures, we demonstrate increased GFA P expression in both adult and young GAERS, suggesting that reactive astroc ytes are already present before the onset of seizures. Glutamate dehydrogen ase (GDH) and glutamine synthetase (GS), which are localized mainly in astr ocytes and involved in glutamate catabolism, are shown to be differentially altered. GDH expression was increased in the thalamus of both young and ad ult GAERS and in the cortex of young GAERS. GS expression was slightly decr eased in the thalamus of young GAERS. These astrocytic modifications are no t adaptive responses to seizures, as the modifications appear before the de velopment of absence seizures, Thus, astrocytes might be involved in the ne uronal processes giving rise to epileptic seizures in this strain. GLIA 32: 15-24, 2000. (C) 2000 Wiley-Liss, Inc.