Abstract
It is well known that limbic seizures are more intractable than neocrotical seizures. This evidence is consistent with our previous finding that the seizure susceptibility produced by limbic kindling was more persistent and potent than that of neocrotical kindling. However, further changes in seizure susceptibility resulting from long-term repetition of generalized convulsion in neocortical kindling remians unclear. In this study, we examined a chronological pattern of seizure susceptibility during 100 days of kindling stimulatins (over-kindling sessions, O-KS) and additional daily stimulations after 100 days of stimulus-free interval in Sylvian or Ectosylvian gyrus kindling in cats. The animals were divided into the following two groups based on the stability of kindled generalized convulsion during O-KS, Group-A (n=4): A stable kindled generalized convulsion appeared after repeated stimulations, and Group-B (n=8): the appearance of generalized convulsions was unstable during O-KS. There was no difference in afterdischarge threshold, kindling rate, location of the electrodes in the temporal cortex, or duration ofgeneralized convulsions between these two groups. Interictal spike discharges were recorded only in group-A after 100 days of resting period. Stage-5 generalized convulsions appeared at the first stimulation of R-KS in 4/4 of group-A and 4/5 of group-B. The most dramatic finding was an appearance of recurrent spontaneous generalized or partial seizures originating in the opposite hemisphere or limbic system, which appeared in 3/4 cats in group-A, but none in group-B. These results suggest that a persistent, solid epileptogenecity can be established after repeated generalized convulsions in neocortical kindling, and that secondary epileptogenic change in the limbic system may play a role in it.
