The effect of direct current field polarity on recovery after acute experimental spinal cord injury

Recent evidence indicates that direct current (DC) fields promote recovery of acutely injured central and peripheral nervous system axons. The polarity of the applied DC field may play an important role in modulating these effects. In the present study, the effect of DC field polarity on recovery of injured spinal cord axons was examined anatomically, electrophysiologically and behaviourly in a rat model. After a 53 g clip compression injury of the cord at T1, 30 adult rats were randomly and blindly allocated to one of three groups (n = 10 each): one group received implantation of a DC stimulator (14 microA) with the cathode caudal to the injury site; the second group received implantation of a similar stimulator with the cathode rostral to the injury site; and the third group received a sham (O microA) stimulator. Clinical neurological function was assessed by the inclined plane technique and axonal function was assessed by motor- and somatosensory-evoked potentials (MEP and SSEP). A quantitative assessment of axonal integrity was performed by counting neurons in the brain retrogradely labelled by the axonal tracer horseradish peroxidase (HRP) and by counting axons at the injury site. The inclined plane scores (P less than 0.0001), MEP amplitude (P less than 0.02), counts of neurons retrogradely labelled by HRP (P less than 0.0001), and axon counts at the injury site (P less than 0.01) were significantly greater in the group treated with a DC field with the cathode caudal to the lesion than in the other two groups. Conversely, the cathode rostral DC field caused a decrease in the number of neurons retrogradely labelled by HRP (P less than 0.05) compared to the sham and cathode caudal groups. These data confirm our previous finding that DC fields promote recovery of acutely injured spinal cord axons. Furthermore, the polarity of the applied field is of critical importance to this effect.

[1]  James M. Kerns,et al.  An experimental implant for applying a DC electrical field to peripheral nerve , 1987, Journal of Neuroscience Methods.

[2]  A. Blight,et al.  Cellular morphology of chronic spinal cord injury in the cat: Analysis of myelinated axons by line-sampling , 1983, Neuroscience.

[3]  D. Gwyn,et al.  Descending nerve tracts in the spinal cord of the rat. I. Fibers from the midbrain , 1969, The Journal of comparative neurology.

[4]  W. Freed,et al.  Promoting functional plasticity in the damaged nervous system. , 1985, Science.

[5]  M. Zanakis,et al.  The short-term effects of delayed application of electric fields in the damaged rodent spinal cord. , 1989, Neurosurgery.

[6]  H. Strahlendorf,et al.  Stimulation of sciatic nerve regeneration in the adult rat by low-intensity electric current , 1987, Experimental Neurology.

[7]  C. McCaig.  Nerve growth in a small applied electric field and the effects of pharmacological agents on rate and orientation. , 1990, Journal of cell science.

[8]  A. Blight,et al.  Functional recovery after spinal cord hemisection in guinea pigs: The effects of applied electric fields , 1990, The Journal of comparative neurology.

[9]  M. Zanakis.  Differential effects of various electrical parameters on peripheral and central nerve regeneration. , 1990, Acupuncture & electro-therapeutics research.

[10]  M. Murray,et al.  Plasticity of spinal systems after unilateral lumbosacral dorsal rhizotomy in the adult rat , 1991, The Journal of comparative neurology.

[11]  A. Blight,et al.  Morphometric analysis of experimental spinal cord injury in the cat: The relation of injury intensity to survival of myelinated axons , 1986, Neuroscience.

[12]  K. R. Robinson,et al.  The distribution of free calcium in transected spinal axons and its modulation by applied electrical fields , 1990, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[13]  M. Fehlings,et al.  The relationships among the severity of spinal cord injury, motor and somatosensory evoked potentials and spinal cord blood flow. , 1989, Electroencephalography and clinical neurophysiology.

[14]  W. Schlaepfer.  Calcium-induced degeneration of axoplasm in isolated segments of rat peripheral nerve. , 1974, Brain research.

[15]  M. Fehlings,et al.  The effect of direct-current field on recovery from experimental spinal cord injury. , 1988, Journal of neurosurgery.

[16]  B. Albala,et al.  Mammalian optic nerve regeneration following the application of electric fields. , 1988, The Journal of trauma.

[17]  R B Borgens,et al.  Enhanced spinal cord regeneration in lamprey by applied electric fields. , 1981, Science.

[18]  L. Jaffe,et al.  Neurites grow faster towards the cathode than the anode in a steady field. , 1979, The Journal of experimental zoology.

[19]  M. Fehlings,et al.  Effect of a direct current field on axons after experimental spinal cord injury. , 1989, Canadian journal of surgery. Journal canadien de chirurgie.

[20]  R. Hall,et al.  Organization of motor and somatosensory neocortex in the albino rat , 1974 .

[21]  A. Blight,et al.  Transected dorsal column axons within the guinea pig spinal cord regenerate in the presence of an applied electric field , 1986, The Journal of comparative neurology.

[22]  B. Pomeranz,et al.  Application of weak electric field to the hindpaw enhances sciatic motor nerve regeneration in the adult rat , 1987, Brain Research.

[23]  V. Lee,et al.  Direct extracellular electrical stimulation influences density dependent aggregation of fetal rat cerebrocortical neurons in vitro , 1988, Neuroscience Letters.

[24]  H. M. Murray,et al.  Origin of the rubrospinal tract of the rat , 1979, Neuroscience Letters.

[25]  J. Kiernan.  HYPOTHESES CONCERNED WITH AXONAL REGENERATION IN THE MAMMALIAN NERVOUS SYSTEM , 1979, Biological reviews of the Cambridge Philosophical Society.

[26]  B. Albala,et al.  Facilitated regeneration in the rat peripheral nervous system using applied electric fields. , 1988, The Journal of trauma.

[27]  S. Wise,et al.  The motor cortex of the rat: Cytoarchitecture and microstimulation mapping , 1982, The Journal of comparative neurology.

[28]  W. Schlaepfer,et al.  Characterization of the calcium-induced disruption of neurofilaments in rat peripheral nerve , 1979, Brain Research.

[29]  G. W. Snedecor.  Statistical Methods , 1964 .

[30]  V. Krauthamer,et al.  Modulation of conduction at points of axonal bifurcation by applied electric fields , 1990, IEEE Transactions on Biomedical Engineering.

[31]  C. McCaig.  Spinal neurite reabsorption and regrowth in vitro depend on the polarity of an applied electric field. , 1987, Development.

[32]  H. W. Beams,et al.  In vitro control of growing chick nerve fibers by applied electric currents. , 1946, Journal of cellular and comparative physiology.

[33]  M. Cohen,et al.  Modification of retrograde degeneration in transected spinal axons of the lamprey by applied DC current , 1983, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[34]  J. Saint-Cyr,et al.  Assessment of spinal cord injury by counting corticospinal and rubrospinal neurons , 1987, Brain Research.

[35]  M. Fehlings,et al.  Motor and somatosensory evoked potentials recorded from the rat. , 1988, Electroencephalography and clinical neurophysiology.

[36]  Charles Tator,et al.  Recovery of spinal cord function induced by direct current stimulation of the injured rat spinal cord. , 1987, Neurosurgery.

[37]  R B Borgens,et al.  Behavioral recovery induced by applied electric fields after spinal cord hemisection in guinea pig. , 1987, Science.

[38]  C H Tator,et al.  Objective clinical assessment of motor function after experimental spinal cord injury in the rat. , 1977, Journal of neurosurgery.