Modulation of excitability by continuous low- and high-frequency stimulation in fully hippocampal kindled rats

• Four-contact desynchronizing LFS consistently increased AD threshold for a period of 2 days to 2 weeks.
• Four-contact desynchronizing HFS significantly decreased AD duration 24 hours following the stimulation period.
• No behavioral seizure alteration occurred in any stimulated group.

SummaryBackgroundLow- and high-frequency stimulation (LFS and HFS, respectively) have been, reported to modify seizure characteristics in rats. We here report effects of hippocampal LFS and HFS, applied at two or four sites in fully kindled rats.MethodsRats were kindled through a hippocampal tetrode until the fully kindled state. Animals with, stable afterdischarge (AD) threshold were randomly assigned to 5 groups; stimulation at 1 Hz (LFS) or, 130 Hz (HFS) was continuously applied for 7 days at 2 or 4 intrahippocampal sites; a control, group received no stimulation. Four-contact stimulation was performed in a rotating fashion. Stimulation effects on AD threshold, AD duration and behavioral seizures were assessed.Key findings: Four-contact LFS consistently increased AD threshold for a period of 2 days to 2 weeks, whereas 4-contact HFS significantly decreased AD duration 24 hours following the stimulation period. No significant AD modification was observed with either 2-contact stimulation paradigms. No, behavioral alteration occurred in any group.Significance: These findings suggest that effects of hippocampal stimulation depend on frequency and topography of stimulus application. LFS and HFS had anti-epileptic effect on afterdischarges when applied in a rotating pattern. This supports concepts on patterned stimulation to result in desynchronization and anti-kindling effects.

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