The Retrograde Degereration of Rubrospinal Neurons Following the Cervical Spinal Cord Hemisection of Adult Rats - A Quantitative Study
Koistinen, Jeanne M.
MetadataShow full item record
It is well known that spinal cord regeneration is limited in mammals. The limitation has been thought to arise from four major problems: scar tissue formation at the lesion site, the lack of guiding pathways for regenerating axons, the compactness of CNS tissue, and the lack of specificity in the reestablishment of functionally appropriate synapses. Recent studies have shown that many neurons of the red nucleus, whose axons project into the spinal cord as the rubrospinal tract, degenerate following cervical spinal cord hemisection. Thus, it has been ·hypothesized that the loss of neurons in the brain whose axons project into the spinal cord may be another reason for the minimal amount of spinal cord regeneration in mammals. The present study was carried out to quantify the loss of neurons in the red nucleus after spinal cord injury. The spinal cords of adult rats were hemisected at the level of the second cervical vertebra, which transected the rubrospinal axons. The experimental animals were allowed to survive 30-55 days before horseradish peroxidase was injected just rostral to the lesion. Horseradish peroxidase is a neuronal marker which is picked up and transpor~ed to the cell bodies by transected axons. The animals were sacrificed and the number of peroxidase-labeled and unlabeled neurons in the red nuclei were counted. The same procedure was applied to the control animals, which were sacrificed without the extended survival period. The results indicated that 53% of the neurons in the red nuclei of' adult rats degenerate following spinal cord hemisection (p=O.006). These results provide the base for future studies which may be useful in determining whether or not spinal cord regeneration in mammals is also limited by the degeneration of injured neurons in the brain.