ELECTROPHYSIOLOGICAL EVIDENCE FOR THE ANTINOCICEPTIVE EFFECT OF TRANSCUTANEOUS ELECTRICAL-STIMULATION ON MECHANICALLY EVOKED RESPONSIVENESSOF DORSAL HORN NEURONS IN NEUROPATHIC RATS

Using a rat model of peripheral neuropathy induced by a tight ligation of L5-6 spinal nerves, the effects of transcutaneous electrical stimu lation on the mechanical responses of wide dynamic range (WDR) dorsal horn neurons were investigated. The responses of the WDR neurons to bo th the brush and pinch stimuli were found to be enhanced in the neurop athic rats compared to those in the normal rats. These enhanced respon ses were depressed by low-frequency and high-intensity transcutaneous electrical stimulation (2 Hz, 4-5 mA) applied to the somatic receptive field. The durations of the depressive effects on the brush responses ranged between 30 and 45 min and those on the pinch responses were 60 -90 min. These results imply that the transcutaneous electrical stimul ation used here produces an antinociceptive effect via a depressive ac tion on the enhanced mechanical responsiveness of the spinal neurons i n this rat model of peripheral neuropathy.