Effect of low frequency electrical stimulation on seizure-induced short- and long-term impairments in learning and memory in rats

Kindled seizures can impair learning and memory. In the present study the effect of low-frequency electrical stimulation (LFS) on kindled seizure-induced impairment in spatial learning and memory was investigated and followed up to one month. Animals were kindled by electrical stimulation of hippocampal CA1 area in a semi-rapid manner (12 stimulations per day). One group of animals received four trials of LFS at 30 s, 6 h, 24 h, and 30 h following the last kindling stimulation. Each LFS trial was consisted of 4 packages at 5 min intervals. Each package contained 200 monophasic square wave pulses of 0.1 ms duration at 1 Hz. The Open field, Morris water maze, and novel object recognition tests were done 48 h, 1 week, 2 weeks, and one month after the last kindling stimulation respectively. Kindled animals showed a significant impairment in learning and memory compared to control rats. LFS decreased the kindling-induced learning and memory impairments at 24 h and one week following its application, but not at 2 week or 1 month after kindling. In the group of animals that received the same 4 trials of LFS again one week following the last kindling stimulation, the improving effect of LFS was observed even after one month. Obtained results showed that application of LFS in fully kindled animals has a long-term improving effect on spatial learning and memory. This effect can remain for a long duration (one month in this study) by increasing the number of applied LFS.