Comparison of hippocampal Deep Brain Stimulation with high (130Hz) and low frequency (5Hz) on afterdischarges in kindled rats.

Hippocampal Deep Brain Stimulation (DBS) is proposed as an experimental treatment for refractory epilepsy, but the optimal stimulation parameters are undetermined. High frequency hippocampal DBS at 130Hz is effective in both animals and patients with epilepsy. Low frequency stimulation (approximately 5Hz) is assumed to have anti-epileptic properties but the efficacy is highly debated. This animal study compares the effects of both stimulation modalities in kindled rats. Sprague Dawley rats (n=20) were fully kindled according to the Alternate Day Rapid Kindling-protocol. After a baseline kindling period, rats were divided into a high frequency group (HFS, 130Hz, n=11) and a low frequency group (LFS, 5Hz, n=9), both receiving 10 days of continuous DBS. During and after DBS, the seizure susceptibility of all rats was tested and the characteristics of the afterdischarges (ADs) were compared between both treatments. During HFS, AD threshold was higher (p<0.05) and at the stimulated site, AD latency was longer (p<0.01) than during baseline period. During LFS, a similar but smaller change was observed, but did not reach significance. The duration of the AD was not affected by either HFS or LFS. After termination of HFS, the effects on AD latency and AD threshold recovered to baseline. In conclusion, high frequency stimulation at 130Hz is more effective than LFS (5Hz) in affecting excitability in epileptic rats. This is reflected in a higher AD threshold and longer AD latency during application of stimulation.