Modification of seizure activity by electrical stimulation: I. after-discharge threshold

Rats with multiple recording and stimulating electrodes were stimulated electrically in the amygdala, hippocampus and reticular formation. Intensity of stimulation was varied in a systematic way to determine the threshold at which after-discharges (ADs) were produced in the vicinity of the stimulating electrode. AD thresholds were permanently reduced by 40–60% in the amygdala and 25% in the hippocampus by daily 1 sec bursts of stimulation. The reduction took place with subthreshold as well as suprathreshold stimulation, but not in the absence of stimulation.It was found that the reduction of AD thresholds in the amygdala had no effect on AD thresholds in the contralateral amygdala, septal area or hippocampus. Reduction of AD thresholds in the hippocampus, however, resulted in an increase in the AD threshold in the contralateral hippocampus.