The ontogeny of seizures in a rat model of limbic epilepsy: evidence for a kindling process in the development of chronic spontaneous seizures.

Kindling is an experimental model for epilepsy in which repeated stimuli induce longer electrographic seizures and eventually cause behavioral convulsions. Although kindling has some features that are similar to chronic human epilepsy, it is not known whether this process plays a role in the development of chronic seizure disorders. We have recently described a rat model of chronic spontaneous limbic seizures that has a number of similarities to human limbic epilepsy. To determine whether a kindling process is involved in the ontogeny of the seizures in this animal model, we continuously monitored 16 rats with EEG and closed circuit television until they had experienced a minimum of 5 and as many as 10 seizures following the first motor seizure. All animals had at least one non-motor seizure before the first motor event (mean 5.1 +/- 0.9 S.E.M. initial non-motor seizures, range 1-12). In addition the seizures significantly lengthened in duration with succeeding events (mean 90 s for the first motor seizure to mean 110 s for the tenth subsequent seizure). These data demonstrate that there is a kindling process involved in the early development of chronic limbic seizures.