Differences in mossy fibre sprouting during conventional and rapid amygdala kindling of the rat

The effect of conventional and rapid amygdala kindling on mossy fibre sprouting and on the development of secondary after-discharges in the hippocampus, i.e. recurring after-discharges after the end of primary after-discharges in the amygdala, was investigated. Rapid kindling, i.e. electric stimulation of the amygdala for 10 s every 30 min, induced prolonged secondary after-discharges in the hippocampus, which occurred after the first stimulation, and mossy fibre sprouting. Conventional kindling, i.e. electric stimulation of the amygdala for 1 s once daily, induced secondary after-discharges in the hippocampus only after prolonged motor seizures, but no mossy fibre sprouting. These results suggest that mossy fibre sprouting and the occurrence of secondary after-discharges in the hippocampus are not crucial for conventional amygdala kindling. Rapid kindling induces these epileptogenic changes in the hippocampus very early and may therefore follow a different route of epileptogenesis than conventional kindling.