Effect of different patterns of low-frequency stimulation on piriform cortex kindled seizures

Low-frequency stimulation (LFS) is an antiepileptic and antiepileptogenic electrical stimulation. In this study the effect of changes in some LFS (1 Hz, monophasic square wave) parameters (intensity, pulse duration and train duration) on piriform cortex kindled seizures was investigated both in fully kindled rats and during kindling acquisition. In fully kindled animals, application of different patterns of LFS immediately before kindling stimulation had no significant effect on seizure parameters. However, daily (15 min) application of LFS (0.1 ms pulse duration at intensity equal to after-discharge threshold (ADT) and 1 ms pulse duration at intensity equal to 1/4 ADT) during inter-seizure interval of 7 days significantly reduced the stage 5 duration of the next kindled seizure. Application of the same two LFS protocols for 3 days and 2 weeks had no effect on seizure parameters. The effect of LFS was also tested using different paradigms during kindling acquisition. When LFS (0.1 and 1 ms pulse duration, intensity equal to ADT and 1/4 ADT) was delivered daily after each kindling stimulation, it could significantly decrease after-discharge duration in various days during kindling development. In this experiment, only LFS with 0.1 ms pulse duration and intensity equal to ADT significantly delayed the appearance of seizure stages 1 and 2. According to obtained results, it may be concluded that in fully kindled rats application of different patterns of LFS before kindling stimulation has no anticonvulsant effect, but it can exert an inhibitory effect when applied during an inter-seizure interval of 7 days. In addition, LFS has antiepileptogenic effect during kindling acquisition. These effects depend on the applied LFS parameters (e.g. intensity, pulse duration and train duration).