Anterograde labeling of the corticospinal tract with biotinylated dextran amine in rat

Objective:To explore the applicative value of biotinylated dextran amine(BDA) to anterograde tracing of the cor-ticospinal tract(CST) in rat.Methods:40 SD adult rats were randomly divided into unilateral pyramidotomy group(n=24),sham lesion group(n=8) and normal group(n=8).The unilateral pyramidotomy model was performed on the left pyramid of medulla oblongata.The Rivlin's inclined plane method was used to detect the motor function of the models.Anterograde tracer BDA was injected into the rat sensorimotor cortex of each group to label and reveal the course of CST in the rat central nervous system.Results:The angles of Rivlin's inclined panel test in unilateral pyramidotomy group were significantly less than those of normal group and sham lesion group(P0.05).In normal group and sham lesion group,BDA positive neurons were dis-tributed symmetrically in the pyramid cells of sensorimotor cortex,and BDA positive fibers of pyramid cells passed through the cerebral cortex,internal capsule,cerebral peduncle of midbrain,basilar portion of pons to the pyramid of medulla oblon-gata.At the lower part of the medulla oblongata,most of the BDA positive fibers passed through the pyramidal decussation to the contralateral side,continously descended at the ventral part of posterior funiculus just dorsal to the posterior gray commis-sure and ended at sacral spinal segments.The same results were observed in the brain of the unilateral pyramidotomy group above the level of the transection site.Below the level of the transection site,the BDA positive fibers were seen in the right pyramid of medulla oblongata and the left dorsal funiculus of spinal cord,but the BDA positive fibers in the left pyramid of medulla oblongata and the right dorsal funiculus of spinal cord were not seen.Conclusions:BDA anterograde tracing method can distinctly reveal the corticospinal tract of rats and possesses good applicative value of application for the morphological study of CST injury and repair.