C57BL/6J mice showed decreases in generalized clonic seizure thresholds with repeated flurothyl-induced seizures using 10% flurothyl. A, The latency to a generalized clonic seizure (i.e., GST) on each seizure trial was assessed for C57BL/6J mice by exposure to 10% flurothyl during eight seizure induction trials (1/d). There was a significant decrease in GST following repeated clonic seizures (p < 0.0001) until plateauing on flurothyl trial 4. *Significance (p < 0.0009) compared with other asterisk groups; @significance (p < 0.009) compared with trials 3–8, as determined by Newman–Keuls post hoc comparisons (trial 3 is also significantly different from trials 6–8, p ≤ 0.05). B, Representative hippocampal local field potential recorded from a C57BL/6J mouse exposed to flurothyl expressing a generalized clonic seizure (Grade 1). Bb1, Bb2, Higher-resolution traces are shown for two representative regions of the trace in B. C, The latency to a generalized seizure (GST) on each seizure trial was assessed for C57BL/6J mice by exposure to 100% flurothyl during eight seizure induction trials (1/d). Plots denote mean ± SEM.