| Research Abstract |
It is generally accepted that kindling-induced interictal discharges (IIDs) are almost similar to IIDs of epileptic patients. However, their general characteristics, i.e., whether they reflect an excitatory event or an inhibitory one and how they are generated, are still unknown. In previous studies, we classified kindling-induced IIDs into three types : simple A,simple B and complex. The complex type consisted of two-three simple IIDs, and its frequency was associated with the development of behavioral responses during kindling.
The present experiment was designed to reveal effects of coordinated stimulations triggered by IIDs on epileptogenes induced by hippocampal kindling of the rabbits. Out of 17 animals, ten developed stage 5 convulsions with a mean of 19 stimulations (K group), whereas the remaining did not (IK group). Before daily kindling stimulation, a coordinated stimulation, which was a miniature type of kindling stimulation either driven at random (RS) or triggered by the I
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ID (TS), was applied to generate an afterdischarge while changing stimulus parameters. The final stimulus intensity (voltage*frequency*no.of train) was standardized based on those of kindling and referred to as a standard intensity index (SII). In K group, averaged SIIs were 28(]SY.+-。[)3% (when the stimuli were triggered by simple A type of IIDs : n=7), 32(]SY.+-。[)4% (simple B : n=16) and 39(]SY.+-。[)4% (complex : n=24), while it was 38(]SY.+-。[)5% when applied at random (n=79). Those of IK group were 48(]SY.+-。[)5% (simple A : n=11), 75(]SY.+-。[)4% (simple B : n=4), 42(]SY.+-。[)3% (complex : n=10) and 55(]SY.+-。[)5% (at random : n=52), respectively. The SII differences between TS and RS were -10 to -7% (simple A), -6 to +20% (simple B) and -23 to +1% (complex). Since negative values indicate weaker stimuli to generate afterdischarges than RS intensity whereas positive values do stronger ones, it is concluded that simple B type of IIDs has suppressive effect on seizure susceptibility while simple A and complex IIDs have facilitatory effect. Less
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