Use of c-fos to identify activity-dependent spinal neurons after stepping in intact adult rats.

An investigation of c-fos activation pattern in spinal neurons of intact adult rats after acute bouts of treadmill locomotion.,To map spinal neurons that are involved in quadrupedal treadmill stepping of intact adult rats by using c-fos as a marker.,Los Angeles, CA, USA.,Spinal cord sections of rats that were not stepped (n = 4) were used to map the FOS-positive (+) neurons under basal conditions. The stepped group (n = 16) was placed on a treadmill to step quadrupedally for varying durations to induce c-fos activity. Spinal cord sections of thoracic and lumbar segments of Stp and Nstp rats were processed using a c-fos antibody, choline acetyl transferase and heat shock protein 27 for identifying motoneurons.,Stepping induced a greater number of FOS+ neurons than was observed in rats that did not step on the treadmill. There was a rostrocaudal and a dorsoventral gradient of FOS labeled neurons. The number of FOS+ neurons increased with the duration of treadmill stepping. Significant increases in FOS+ neurons were in the most medial parts of laminae IV, V, and VII. FOS+ motoneurons increased with treadmill stepping, particularly in large motoneurons (> or = 700 microm2).,These data suggest that FOS can be used to identify activity-dependent neuronal pathways in the spinal cord that are associated with treadmill stepping, specifically in lamina VII and in alpha motoneurons.,NIH NS16333, NS40917, and the Christopher Reeve Paralysis Foundation (CRPF VEC 2002).