Modulation of excitability by continuous low- and high-frequency stimulation in fully hippocampal kindled rats
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Figure 1
Mean afterdischarge threshold (ADT) in the different groups before and after one week of stimulation on two (2C) or four (4C) contacts. In the LFS4C group, Post1, Post2 and Post3 values were statistically significantly higher than the mean of Pre values (red star) (p = 0.023 for the three comparisons). The other groups showed no significant differences. Data in μA + 1 standard error.
Figure 2
Mean afterdischarge duration (ADD) in the different groups before and after one week of stimulation on two (2C) or four contacts (4C). The HFS4C group showed a statistically significant decrease in ADD comparing values before and after stimulation (red star), with Post2 being shorter than the mean of Pre values (p = 0.02). No significant changes in ADD were observed in the other groups. Data in seconds + 1 standard error.
Figure 3
Representative LFP recording of two afterdischarges (AD) from a rat in the HFS-4C group, a Pre-SP (up) and a Post-SP (down) stimulation session. This case illustrates the AD duration decrease observed after one week of desynchronizing HFS. Black arrows indicate the AD end. Scale bars in mV and seconds.
Highlights
- •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.
Summary
Background
Low- 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.
Methods
Rats 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.
Keywords:
Kindling, Hippocampus, Low-frequency brain stimulation, High-frequency brain stimulation, Hippocampal stimulation, Multi-site stimulationTo access this article, please choose from the options below
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