Effects of low-frequency repetitive electric and magnetic brain stimulation on somatosensory evoked potentials in rats

Since the mechanism that repetitive electric (rES) or transcranial magnetic stimulation (rTMS) transiently modulates cortical neuron excitabilities is not clear, we studied the effects of rES and rTMS on somatosensory evoked potentials (SEPs) in rats. After anesthetizing rats, a pair of burr holes was drilled in the skull over the right somatosensory area for the hind limb. rES was performed with a frequency of 1 or 0.2 Hz for 3 h and 20 min using two stainless screws inserted into the burr holes. The right somatosensory areas were magnetically stimulated with a frequency of 0.2 Hz for 2 h and 20 min using a small eight-figure coil. SEPs elicited by stimulating the left hind limb was recorded before and after rES or rTMS. Amplitudes and latencies of SEP components were measured and compared between the rES or rTMS and control groups. As a result, amplitudes of cortical components of SEPs were significantly reduced after rES or rTMS compared with those in the control. Amplitudes of other components were not significantly changed by rES or rTMS. The present results support rES and rTMS having similar effects on cortical neuron excitabilities.