[A biphasic changes in the seizure-threshold in kindling seizure development induced with low-frequency electrical...

Seven cats were stimulated once a day with low-frequency electrical stimulations to assess the serial changes of development. Each animal had been implanted stereotaxically with a stimulating electrode into the left-side ventral hippocampus and with recording electrodes into the right-side ventral hippocampus, the bilateral dorsal hippocampus. We applied the stimulations at 10:00 AM, bipolarly with 2 mA-biphasic square-wave pulses (1 msec durations). The pulse-interval was set at 300 msec. If epileptic afterdischarge could not be triggered on EEG with this pulse-interval, a 100msec-interval stimulation was applied after 15 min-rest period. The number of stimulating pulses required for a triggering of afterdischarge was defined as pulse-number threshold (PNT) which was used as an indicator of the seizure-threshold. The duration of each seizure on EEG (afterdischarge duration, ADD) was also recorded and the seizure-related behaviors were classified into 5 stages as follows: 1, staring or immobility; 2 appearance of facial twitching or head nodding ; 3, tonic convulsions of the right-side fore-paw or a head turning toward the right-side; 4, generalized clonic convulsions; 5, generalized convulsions with a falling down. The kindling procedure completed within a mean of 36.5 days, and all the animals presented stage-5 seizures. At the completion of kindling, PNT was determined at 10.5 +/- 1.8 (mean +/- SE). During the kindling process PNT showed a sudden decrease in the initial part of stage-1 (within a mean of 3.8 days) and a gradual increase from stage-3 to stage-5. ADD showed a simple increasing function of the development of seizure-stage.(ABSTRACT TRUNCATED AT 250 WORDS)