Investigating the Effects of Low Frequency rTMS on Kindled Seizure in Rats

 Introduction: Neural stimulation is a promising new technology for the treatment of medically-intractable seizures.  Transcranial Magnetic Stimulation (TMS) is a simple, non-invasive, low cost technique which is widely used in neurophysiology. In a few studies that have been performed at different frequencies the therapeutic effects of this technique were not obvious. Repetition of low frequencies TMS (≤1 Hz) has inhibitory and quenching effects on neuron activities and it decreases the excitability of the cortex. In epilepsy, as a disease of the central nervous system, the excitability of the cortex increases. It seems that such a technique at its optimum frequencies has therapeutic potential in epilepsy. Materials and Methods: In this study, the effect of 0.1, 0.5, 1 and 2 Hz repetitive Transcranial Magnetic Stimulation (rTMS) at an  intensity of  80% Resting Motor Threshold (RMT) and at 1 Hz with an  intensity of  90 and 100% RMT  on Amygdala-kindling model in rats in optimum spatial coordinate was investigated. The procedure includes delivering a daily 5 minute rTMS stimulus using a butterfly figure coil having 25 mm in diameter and the coordinate which induces the maximum electrical field in Amygdala area.  The stimulus was given within five minutes after the electrical kindling stimulus was delivered.  The number of days to reach stage 1, 2, 3, 4 and 5 of kindling model After Discharge Duration (ADD) in each day and the percentage of cumulative ADD between the treated and the control group was statistically compared.  Two groups were used to investigate the effect of the intensity of the magnetic field. A frequency of 1 Hz rTMS at an intensity of 90% and 100% RMT was delivered with the same physical parameters as before. Results: Using a frequency of 1 Hz rTMS at an intensity of 80% and RMT of 90% showed a significant inhibitory effect on the spread of seizure into other areas of brain in comparison to the control group. Increasing the intensity of the magnetic field from 80 to 90% RMT increased the inhibitory effect of this technique.  However, the quenching effect was significantly decreased when the intensity of the magnetic field was increased to 100% RMT. Discussion and Conclusion:  It seems that the frequency of rTMS and Motor Threshold of subject are important factors in causing physiological effects. This study showed that rTMS technique at some frequencies and intensities may have therapeutic effect on epilepsy.