Introduction

Epilepsy is a chronic disorder of the central nervous system characterized by paroxysmal excessive electrical activity and recurrent behavioral seizures. Epilepsy can develop at any time from infancy to old age as a manifestation of genetic, acquired, or degenerative diseases, but it also frequently develops in the absence of overt pathology. Epileptic disorders can be classified into distinct syndromes with specific etiologies and natural histories (Dreifuss et al., 1985). For all of these reasons, epilepsy should not be considered as a single disorder, but as a heterogeneous condition defined by the common features of abnormal electrical activity and recurrent seizures.

The cellular and molecular events that play a role in the generation of seizures and epilepsy have been investigated in experimental models that are as varied and diverse as the clinical phenomena of epilepsy. For example, mechanisms of seizure generation have been studied with electrophysiological methods after acute induction of seizures by drugs that block inhibition, such as penicillin, bicuculline, or picrotoxin (Schwartzkroin & Prince, 1977; Prince, 1978; Hablitz, 1984; Gean & Shinnick-Gallagher, 1987). As the induced seizures cease when the convulsant drugs are withdrawn, the epileptic activity induced by these drugs is more appropriately considered as a model of seizure generation rather than epilepsy, a chronic condition characterized by recurrent seizures that usually occur sporadically and unpredictably over long intervals.