Abstracts

Rationale: Kindling is a widely used animal model of intractable temporal lobe epilepsy. To reveal the underlying mechanism of kindling-induced epileptogenesis, the duration of afterdischarge (AD), the frequency of interictal discharge (IID), and the behavioral response have been examined. In the present study, we examined FFT analysis on kindling-induced AD in the rabbit hippocampus. Methods: Twenty-one adult rabbits were used. Under pentobarbital anesthesia, two pairs of bipolar stainless steel electrodes were implanted in the right dorsal hippopcampus. Kindling stimulation was a train of biphasic pulses (1 ms duration each) of 50 Hz for 1 s, with a suprathreshold intensity for AD. Progressive change of behavioral responses was classified into 5 stages according to the conventional criteria. FFT analysis on each AD was performed with sampling frequency of 1 kHz by Power Lab (Chart, ADInstrument). Results: Out of 21 animals, 13 developed stage 5 convulsions with a mean of 18 stimulations (Kindled (K) group), whereas the remaining 8 animals did not (Incomplete kindling (IK) group). FFT analysis showed a different property between K and IK group. In IK group, the peak frequency at 3-7 Hz was characterized during the whole course of kindling where the animal kept the stage 2 or 3 behavioral responses (Fig. 1A). In K group, the peak frequency at 3-7 Hz also appeared during early phase of kindling (stage 1-2), but two peaks at 3-7 and 15-30 Hz appeared during late phase (stage 3-5) (Fig. 1B). The shift from one- to two-peak FFT pattern was closely related to the enhancement of behavioral responses and to the increment of complex IID frequency during kindling. Conclusions: We conclude that different FFT patterns of AD appear during the uni-lateral kindling of the rabbit hippocampus and the second fast component (15-30 Hz) has an important role in kindling progression. Relationships among AD duration, IID frequency, behavioral response and FFT pattern will be discussed.