Effect of priming low-frequency magnetic fields on zero-Mg2+ -induced epileptiform discharges in rat hippocampal slices

Abstract

During the process of seizures, the addition of low-frequency magnetic fields has been proved to be an effective method to suppress epileptic discharges. However, whether adding magnetic fields before the appearance of epileptic discharges can produce this inhibition has not been studied. In the present study, we first constructed epilepsy models on brain slices by perfusing them with Mg2+-free artificial cerebrospinal fluid (aCSF). The events of seizures evolved from inter-ictal epileptiform discharges (IIDs) to inter-epileptiform discharges (IDs). Combined with the multi-electrode array platform, we designed a flexible moving coil to generate a 0.5 Hz magnetic field on the brain slices. Using this method, we added the magnetic fields to brain slices for 30 min before epileptiform discharges were induced. The experimental results demonstrated that although the priming magnetic fields could not completely inhibit epileptiform discharges, they can significantly reduce the frequency of IDs and increase the frequency of IIDs in the CA3 region of the hippocampal slices. In the control group, the rates of IDs and IIDs were 0.0024 ± 0.0006 Hz and 0.0138 ± 0.0043 Hz, respectively, while in the magnetic stimulation group, the rates were 0.0012 ± 0.0004 Hz and 0.0251 ± 0.0067 Hz. Moreover, the results indicated that changing the frequency of interictal discharges did not affect ictogenesis. The results demonstrated that the priming magnetic fields had a certain weakening effect on the frequency of IDs, which was achieved by reducing the signal propagation speed and increasing the excitability threshold of hippocampal neurons.