Affiliations: Institute of Neurosciences, The Fourth Military
Medical University, Xi'an, 710032, China
Note: [] Corresponding author: Gong Ju, Institute of Neurosciences, The
Fourth Military Medical University, 17 Changlexi Road, Xi'an 710032, P.R.
China. Tel.: +86 29 3220448; Fax: +86 29 3246270; E-mail: jugong@fmmu.edu.cn
Abstract: Purpose: A major issue in analysis of experimental results after
spinal cord injury is spontaneous functional recovery induced by remaining
nerve fibers. The authors investigated the relationship between the degree of
locomotor recovery and the percentage and location of the fibers that spared
spinal cord transection. Methods: The spinal cords of 12 adult rats were transected at T9
with a razor blade, which often resulted in sparing of nerve fibers in the
ventral spinal cord. The incompletely-transected animals were used to study the
degree of spontaneous recovery of hindlimb locomotion, evaluated with the BBB
rating scale, in correlation to the extent and location of the remaining
fibers. Results: Incomplete transection was found in the ventral spinal cord
in 42% of the animals. The degree of locomotor recovery was highly correlated
with the percentage of the remaining fibers in the ventral and ventrolateral
funiculi. In one of the rats, 4.82% of remaining fibers in unilateral
ventrolateral funiculus were able to sustain a certain recovery of
locomotion. Conclusions: Less than 5% of remaining ventrolateral white matter is
sufficient for an unequivocal motor recovery after incomplete spinal cord
injury. Therefore, for studies with spinal cord transection, the completeness
of sectioning should be carefully checked before any conclusion can be reached.
The fact that the degree of locomotor recovery is correlated with the
percentage of remaining fibers in the ventrolateral spinal cord, exclusive of
most of the descending motor tracts, may imply an essential role of
propriospinal connections in the initiation of spontaneous locomotor
recovery.
Keywords: spinal cord transection, remaining spinal fibers, white matter, ventrolateral funiculus, locomotion, rat
