Scope and contribution of genetic models to an understanding of the epilepsies.

Studies of the genetic models of the epilepsies emphasize that some seizure disorders result from an aberrant "wiring diagram" coupled with abnormal activity of individual neurons. These defects cause the unique seizer-triggering mechanisms operative within the epileptic nervous system but which are inactive or do not exist in normal subjects. Moreover, causes of epilepsy reside not only within the brain area, wherein initial appearance of epileptic EEG discharge occurs, but also outside that region. Etiologically significant neurochemical dysfunctions may be common features of the epileptic condition in genetic models across species. Accordingly, genetically determined convulsive epileptogenesis in rats, baboons, and humans may result partially from noradrenergic and GABAergic deficits. In contrast, genetically derived absence seizures in the rat and perhaps also humans may occur in response to GABAergic excess. The unique features of the genetically epileptic animals emphasize their usefulness in developing novel drugs that selectively ameliorate seizure predisposition.