Evaluation of low frequency stimulation in fully kindled rats

To evaluate the potential of stimulation techniques to suppress epileptic activity, human studies are limited regarding the analysis of stimulation parameters. Animal models can serve for a systematic study of the efficacy of different stimulation paradigms. Earlier studies demonstrated that in animal models of kindling, short term low frequency stimulation (LFS) applied during the kindling process is able to interfere with epileptogenesis. We here studied the effects of LFS after consolidation of the epileptogenic process. Wistar rats underwent hippocampal kindling (60Hz, 1.6s, 500μA, once daily stimulation) until reaching the fully kindled state. Stimuli to evoke seizures were then adjusted to individual afterdischarge (AD) thresholds. Animals were then submitted to infrathreshold short term LFS protocol delivered through 4 electrodes on the ipsilateral hippocampus using bipolar stimulation (alternating between each pair of electrodes) with square waves at 1Hz, 50-150μA, 15 minutes per day for 7days. The AD latency was significantly longer after the LFS application and a statistically nonsignificant increase tendency was also observed on the AD threshold and AD duration. The AD amplitude and the behavioural seizure duration were not significantly influenced. These data suggest that short term infrathreshold LFS is not able to suppress continued ictogenesis in fully kindled rats.