Effect of TENS-like stimulation on C afferent-induced c-fos expression in the rat spinal cord

Transcutaneous electrical nerve stimulation (TENS) has been widely used to relieve pain. This study examined the effect of TENS-like stimulation on primary C afferent-induced c-fos expression in the rat spinal dorsal horn. Fos-like immunoreactivity (FLI) evoked by excitation of C fibres of the tibial nerve was found ipsilaterally in laminae I-VIII and X of the spinal cord. The greatest number of FLI neurones was located in the medial half of laminae I-II0 and V at L5. When TENS-like stimulation (100 Hz) was applied proximally to the same tibial nerve, the number of FLI neurones by C afferents was reduced remarkably in ipsilateral laminae I-II0 and IV-VII. The results suggest that TENS stimulation-induced reduction of c-fos expression may reflect an inhibition of spinal nociception.