Hippocampal kindling facilitates amygdala-kindled seizures in rats

  In this study, the effect of an experimentally increased excitability in hippocampal neurons, via hippocampal kindling, on amygdala kindling rate was investigated in rats. Animals were divided into 4 groups. In all groups, except group 2, tripolar electrodes were implanted in the amygdala and CAI region of the dorsal hippocampus. Group 2 animals were only implanted with tripolar electrodes in the amygdala. In group 1, the rats were kindled one week after surgery, first from the hippocampus, then by amygdala stimulation the next day. In groups 2 and 3, rats were kindled one week after surgery from the amygdala. Group 4 animals had a recovery period of one week plus 32 days, which was the mean of the hippocampal kindling rate in group 1, and then they were kindled from the amygdala. In group 1, the amygdala kindling rate (n number of stimulation trials that must be administered before the stage 5 motor convulsion is triggered) was significantly facilitated and seizure at day n/2 during amygdala kindling was significantly increased. There was also a significant positive correlation between hippocampal and amygdala kindling rates. Results obtained in the present study show that an increase in hippocampal excitability in group 1 could facilitate kindling from the amygdala. Thus it may be suggested that the hippocampus has an important role in the development and propagation of seizures from the amygdala.