Developing genetically epilepsy-prone rats have an abnormal seizure response to flurothyl.

Development of clonic-tonic flurothyl-induced seizures was examined in both normal and genetically epilepsy-prone rats (GEPRs). At each age, from 10 to 30 days, clonus occurred at significantly shorter latencies in GEPRs than in normal rats. The latency to onset of clonic seizures did not change with age, however, in either GEPRs or normal rats. A different pattern of response was observed in the progression to tonic seizures. As normal animals matured, the latency to tonic seizures became longer and, by day 30, the duration of flurothyl exposure necessary to induce tonus was almost 70% greater in normal rats than in the GEPRs. In contrast, in GEPRs, tonic extension occurred immediately following the onset of clonus throughout development. A subset of GEPRs failed to have audiogenic seizures in a 40-day posttest. These animals had a flurothyl response identical to their audiogenic-susceptible litter mates. These data suggest that (a) a protective mechanism which develops against tonic seizures in normal rats fails to mature in the GEPR, and (b) seizure inducing gene-linked neural abnormalities occur in the GEPR independent of pathologies underlying audiogenic seizures.