GABA neurons in seizure disorders: a review of immunocytochemical studies.

Immunocytochemical studies have identified alterations in GABA neurons in several models of seizure disorders. However, the changes have varied among different epilepsy models, and these variations presumably reflect the diversity of mechanisms that can lead to seizure disorders. In models of cortical focal epilepsy, there is strong evidence for decreases in the number of GABAergic elements, and the changes closely parallel the time course of seizure development. By contrast, in some genetic models of epilepsy, increases in the number of immunocytochemically-detectable neurons have been observed in selected brain regions. In several models of temporal lobe epilepsy, there presently is little immunocytochemical evidence for alterations of GABA neurons within the hippocampal formation despite physiological demonstrations of decreased GABA-mediated inhibition in this region. However, it remains possible that certain types of GABA neurons could be differentially affected in some seizure disorders while other types are preserved. Thus, distinguishing between different classes of GABA neurons and determining their functional roles represent major challenges for future studies of GABA neurons in seizure disorders.