A new model of petit mal epilepsy: spontaneous spike and wave discharges in tremor rats.

A mutant rat, which was found in a colony of Kyoto:Wistar rats and genetically defined as a tremor rat (tm/tm), developed tremor of the whole body at 2 weeks of age but the tremor gradually disappeared between 6 and 8 weeks of age. The electroencephalogram (EEG) recorded using chronically implanted electrodes showed a 5-7 Hz (mostly 6 Hz) spike and wave complex synchronously in the cerebral cortex and hippocampus accompanied by absence-like seizure in all six tremor rats examined. The spike and wave complex appeared 0.8-1.9 times per minute and lasted for 1-17 s. However, normal EEG activity was observed in the intervening periods, free of absence-like seizure. Thus the tremor rat is considered to be a possible model for studying the pathogenesis and therapy of petit mal epilepsy in humans.