Interruption of the dorsal corticospinal tract (CST) after spinal cord injury (SCI).

<p><b>A</b>. Hindlimb CST axons were labeled by injecting biotinylated dextran amine (BDA) into 9 sites in the hindlimb motor area of each hemisphere 4 weeks after SCI. Rats survived 2 more weeks to allow for BDA transport. <b>B</b>. Identity of brain structures (from the atlas of Paxinos and Watson, 1997). <b>C</b>. Parasagittal section through the thoracic cord shows labeled CST axons (<i>arrowhead</i>) rostral to the lesion (<i>dashed lines</i>). Note the absence of labeled fibers distal to the injury. <b>D</b>, <b>E</b>. Transverse sections of the spinal cord at the cervical (<b>D</b>) and lumbar (<b>E</b>) enlargements. Note heavy labeling at the cervical level (<b>D</b>, <b>D</b>') but absence of labeling in the lumbar cord (<b>E</b>, <b>E</b>'). Scale bar, 500 µm.