Spared Corticospinal Tract Projections Through Lateral Funiculi after Dorsal Section of the Rat Mid-thoracic Spinal Cord

Kim, Sang Soo; Shim, Dae Moo; Kim, Jong Hwan; Song, Ha Hun; Kim, Joung Woo; Kim, Tae Geun

Abstract

In the rat lumbar spinal cord, the pathways and distribution of corticospinal tract (CST) axons were investigated using retrograde transport of Fast Blue(FB) and Fluoro-Gold(FG). The purpose of this study was, therefore, to fond the extent of CST projections in the lateral funiculus in the rat. Total of twelve female rats were used in this study. The laminectomy was performed at the 78 cord level to expose the spinal cord. Using a radiofrequency lesioning device, the CST, including the dorsal columns, were lesioned bilaterally. Three to seven days after lesioning, two laminectomies were performed at C6-8 and L3-5 to expose the spinal cord for dye injections. Retrograde tracing of fast blue(FB) and fluoro-gold(FG) were used to quantitate the number of cerebral cortex neurons projecting to the lumbar cord through tracts other than the CST in the dorsal column. New findings of the this study are : (1) a small number of CST axons projected to lumbosacral spinal cord bilaterally in the dorsolateral funiculi. (2) some axons projecting to the lumbar cord through the dorsolateral funiculi are collateral of neuron that project to the cervical spinal cord. Our results suggest that there are a larger number of CSTs than previously thought projecting to the lumbar spinal cord through the lateral funiculi. These residual tracts may play a role in the functional recovery of the affected limbs.