Fig. 1. Pruning of collaterals occurs between 10 and 28 days after spinal cord injury (SCI).

a Experimental scheme. Dorsal hemisection or laminectomy alone was conducted at T8 level in mice. An anterograde tracer, biotinylated dextran amine (BDA), was then injected into the hindlimb motor area to label the collaterals from corticospinal tract (CST). Mice were perfused at 10 or 28 days after SCI. The number of collaterals at the cervical cord (C4-7) was histologically assessed. b-d Transverse cervical sections showing BDA-labeled CST axons (green) in sham mice (b) and injured mice at 10 days (c) and 28 days (d) after SCI. White arrows indicate collaterals sprouted from CST. Scale bar: 200 μm. e Quantification of the number of collaterals. The total number of collaterals from C4 to C7 was divided by the number of main CST fibers running in the dorsal column. It was increased at 10 days after SCI and decreased at 28 days after SCI. Data are presented as mean ± SEM. n = 3–6, **p < 0.01,*p < 0.05, one way ANOVA followed by Tukey-Kramer test