Effect of alternating current stimulation of the spinal cord on recovery from acute spinal cord injury in rats

Abstract

The therapeutic value of electrical stimulation of the spinal cord was studied in rats injured by acute compression of the spinal cord. Twenty adult Wistar rats underwent cord compression at T6–7 by the extradural clip compression technique at a force of 125 g for 1 minute. After injury and group randomization, stimulating electrodes were placed extradurally, proximal and distal to the injury site, and attached to a small, implantable receiver-stimulator. The receiver was secured to the paraspinal muscles and implanted subcutaneously, overlying the thoracic spine. The animals were maintained in specially designed cages with encircling antennae attached to radio frequency transmitters. The 10 treatment animals were subjected to a 460-kHz electromagnetic field, pulsed at a frequency of 10 Hz. The receivers converted the pulsed radio frequency into square-wave pulses at the cord electrodes (width 1 ms, frequency 10 Hz). The 10 control animals were exposed to a similar field but with a frequency below the range of the tuned receiver, and therefore they did not receive the square-wave pulse. Clinical recovery was assessed by the inclined plane technique which measures the maximum angle of inclination attained without falling. After 15 weeks of continuous spinal cord stimulation, the inclined plane performance was not significantly different between the two groups (treatment group mean, 44.4 ± 5.4; control group mean, 41.7 ± 7.9). This is the first experimental study of the effect of long-term continuous electrical stimulation on spinal cord recovery in mammals. The methods required and the technical aspects involved in achieving continuous stimulation, and the guidelines for future study of this modality are discussed.