The Effects of Repetitive Transcranial Magnetic Stimulation on Picrotoxin-Induced Convulsions in Mice.

Background: Clinical and experimental results show that repetitive transcranial magnetic stimulation (rTMS) is effective and safe in the treatment of epilepsy. The characteristics of the impulse magnetic field (IMF) are empirical in these studies, making impossible to compare their effectiveness.

Objectives: The article presents the results of a study of the anticonvulsive effects of different modes of IMF on the picrotoxin seizure model, which is important for studying GABAergic brain mechanisms activated by rTMS.

Material And Methods: The experiments were performed on outbred male mice (n = 597; 450 in the experimental group and 147 in the control group). The picrotoxin was injected in a dose of 2.5 mg/kg subcutaneously after either rTMS or a placebo. The rTMS regimes varied in frequency (0.1, 0.3, 0.5, 1.0 and 10 Hz), intensity (10, 20 and 40% of maximal magnetic induction [MMI] of the big ring coil) and the number of procedures (1, 3, 10). The dependence of the criterial characteristics on the TMS parameters was shown in this convulsive model.

Results: The analysis of the data obtained showed that 10 rTMS sessions at an intensity of 20% of MMI in the range of frequencies from 0.5 to 1.0 Hz had the most stable and significant effect in terms of reducing the convulsive readiness of the brain, evaluated by the latent period of the myoclonuses in the picrotoxin test. In all the regimes of exposure, rTMS decreased the number of seizures in the picrotoxin model by 1.5-2 points; the most significant effect was obtained with 10 rTMS sessions in the 0.5-1.0 Hz frequency range and an intensity of 20% of the MMI (р < 0.01).

Conclusions: The study results support the use of IMF as therapy for blocking convulsive attacks.