Abstracts

It has been reported that spike-and-wave discharges are consistenly recorded from the thalamus and the cortex whereas no spike-and-wave discharges are recorded from the limbic structures including the amygdala and the hippocampus in genetic absence epilepsy rats from Strasbourg (GAERS). Therefore, limbic structures are not generally considered to involve in the pathogenesis of absence epilepsy. In this study we aimed to evaluate electroencephalogram (EEG) from the cortex and amygdala of GAERS before and after repeated kindling electrical stimulations. Electrodes were stereotaxically implanted into the basolateral amygdala of GAERS (n=12) for stimulation and recording and into the cortex for recording. After a recovery period, in order to determine the afterdischarge threshold, the basolateral amygdala of the rats was stimulated with an initial stimulation of 50 [micro]A (monophasic, square wave pulses of 80 Hz, each 1 msec in duration, for a total duration of 2 seconds) and continued with 50 [micro]A increments until an initial afterdischarge was obtained. Next, the animal was stimulated twice daily at the current afterdischarge threshold. The maximum number of electrical stimulations was 30. EEG was recorded to analyze spike-and-wave discharges and afterdischarge durations. All GAERS showed cortical spike-and-wave discharges in the basal EEG before kindling stimulations. Nine out of 12 GAERS demonstrated no spike-and-wave discharges in the basolateral amydala with the maximum number of kindling stimulations. On the other hand, the basolateral amygdala recording of 3 GAERS with repeated electrical stimulations showed spike-and-wave discharges in EEG while their basal EEG before the kindling process demonstrated no spike-and-wave discharges in the basolateral amygdala. In addition, repeated amygdala kindling stimulations significantly enhanced the amplitude of spike-and-wave discharges in the EEG of 3 GAERS. Although limbic structures are not generally thought to contribute to the brain circuitry in which spike-and-wave discharges are generated, the observation of spike-and-wave discharges in the basolateral amygdala suggest that in a subpopulation of GAERS the amygdala seems to be involved in the generation of spike-and-wave discharges. (Supported by Marmara University Scientific Research Committee (BAPKO).)