The suppressive effect of electrical stimulation on nociceptive responses in the rat.

BACKGROUND AND PURPOSE The aim of this investigation was to study the effect of electrical stimulation on nociceptive responses within the lumbar levels of the rat spinal cord. METHODS A single high-energy thermal pulse produced by a surgical laser stimulator (5 W, 30 milliseconds) was applied on the plantar surface of the hind paws of male Sprague-Dawley rats. The spinal cord field potential evoked by the laser pulse was used as an indicator of thermosensitive nociceptive responses. Low-intensity single stimulation, high-intensity single stimulation, low-intensity train stimulation, and high-intensity train stimulation were applied on the common peroneal nerve with protected cuff electrodes in different trials. RESULTS Neither low-intensity nor high-intensity single stimulation suppressed field potentials. In contrast, low-intensity train stimulation elicited partial inhibition of field potentials. Furthermore, high-intensity train stimulation elicited biphasic inhibition at a wider range of intervals lasting for 20 seconds. CONCLUSION AND DISCUSSION The results demonstrate that two modes of train electrical stimulation can produce two patterns of fast-onset (within milliseconds), short-duration (within 20 seconds) inhibition of field potentials in the spinal cord. These results provide evidence that noxious heat-related impulses are modulated by the presence of specific electrical stimulation. The clinical application of transcutaneous electrical nerve stimulation to block pain is supported.