Quadrupedal treadmill stepping increases the number of FOS+ neurons. Immunostained L5 spinal cord section with c-fos antibody (a). Dashed line designates the contrast between the nonstepped (Nstp) and stepped (Stp) rat spinal cord. DH = dorsal horn, CC = central canal, VH = ventral horn. Scale bar = 100 μm. FOS+ neurons tagged in sections shown in (a) with ImagePro Plus software (b). The symbols indicate intensity of FOS staining; high (○), medium (□), low (△). The black line outlines the gray matter. Scale bar = 100 μm. Treadmill stepping for 60 min increased the number of FOS+ neurons of all segments of spinal cord T13–L6 (c), and in all spinal cord laminae I–X (d) of Stp rats compared to Nstp rats and laminae IV, V, and VII are significantly higher than other laminae within Stp rats (asterisks)