Effect of repeated transcranial magnetic stimulation during epileptogenesis on spontaneous activity of hippocampal CA1 pyramidal neurons in rats

Introduction: Considering the antiepileptogenic effects of repeated transcranial magnetic stimulation (rTMS), the effect of rTMS applied during amygdala kindling on spontaneous activity of hippocampal CA1 pyramidal neurons was investigated. Materials and Methods: A tripolar electrode was inserted in basolateral amygdala of Male Wistar rats. After a recovery period, animals received daily kindling stimulations until they reached stage 5 seizure. In one group of animals, rTMS at frequency of 1 Hz were applied to hippocampus once daily at 5 min after termination of kindling stimulations. 24 h after the last kindling stimulation, spontaneous activity of CA1 pyramidal neurons of the hippocampus was investigated using whole cell patch clamp technique. Results: Kindling-induced seizures resulted in increment of spontaneous activity of hippocampal CA1 neurons, but application of rTMS during amygdala kindling prevented it. Moreover, rTMS administration inhibited the kindling-induced enhancement of afterdepolarization (ADP) amplitude and action potential duration. Conclusion: Results of this study suggest that rTMS exerts its anticonvulsant effect, in part, through preventing the amygdala kindling-induced increase in spontaneous activity and excitability of hippocampal CA1 pyramidal neurons.