The injured spinal cord spontaneously forms a new intraspinal circuit in adult rats

Nat Neurosci. 2004 Mar;7(3):269-77. doi: 10.1038/nn1195. Epub 2004 Feb 15.


In contrast to peripheral nerves, central axons do not regenerate. Partial injuries to the spinal cord, however, are followed by functional recovery. We investigated the anatomical basis of this recovery and found that after incomplete spinal cord injury in rats, transected hindlimb corticospinal tract (CST) axons sprouted into the cervical gray matter to contact short and long propriospinal neurons (PSNs). Over 12 weeks, contacts with long PSNs that bridged the lesion were maintained, whereas contacts with short PSNs that did not bridge the lesion were lost. In turn, long PSNs arborize on lumbar motor neurons, creating a new intraspinal circuit relaying cortical input to its original spinal targets. We confirmed the functionality of this circuit by electrophysiological and behavioral testing before and after CST re-lesion. Retrograde transynaptic tracing confirmed its integrity, and revealed changes of cortical representation. Hence, after incomplete spinal cord injury, spontaneous extensive remodeling occurs, based on axonal sprout formation and removal. Such remodeling may be crucial for rehabilitation in humans.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Axotomy
  • Cell Differentiation / physiology
  • Electromyography
  • Female
  • Growth Cones / physiology
  • Growth Cones / ultrastructure
  • Hindlimb / innervation
  • Interneurons / physiology
  • Interneurons / ultrastructure
  • Motor Cortex / cytology
  • Motor Cortex / growth & development
  • Motor Neurons / cytology
  • Motor Neurons / physiology
  • Nerve Regeneration / physiology*
  • Neural Conduction / physiology
  • Neuronal Plasticity / physiology*
  • Presynaptic Terminals / physiology
  • Presynaptic Terminals / ultrastructure
  • Pyramidal Tracts / cytology
  • Pyramidal Tracts / growth & development*
  • Rats
  • Rats, Inbred Lew
  • Recovery of Function / physiology*
  • Spinal Cord / cytology
  • Spinal Cord / growth & development*
  • Spinal Cord Injuries / physiopathology*
  • Spinal Cord Injuries / therapy