Delayed application of direct current electric fields in experimental spinal cord injuries

The cutaneus trunci muscle (CTM) reflex of guinea pigs depends on an ascending afferent pathway within the ventrolateral funiculus of the thoracic spinal cord. The expression of this reflex is a phasic contraction of back skin in response to tactile stimulation, which is permanently eliminated by transection of the ventrolateral funiculus. It was shown previously that when a polarized (rostrally negative), weak (300-400 μV/mm) DC electric field is placed across a lateral hemisection of the spinal cord in adult guinea pigs at the time of injury, approximately 13% recover the reflex, while sham-treated animals remain unchanged. In this study, a similar approach was used, except that three months were allowed to pass between the time of hemisection and experimental treatment. No recovery of the CTM reflex was observed in 13 animals with rostrally negative fields, 8 of which were followed for at least 9 months, 5 for 3 months; or in 11 animals with caudally negative applied fields, 8 of which were followed for 9 months and 3 for 3 months.