Figure 3

Double labeling of regenerating radial nerve cords for the fibers expressing the neuropeptide GFS and proliferating cells with BrdU. Longitudinal tissue sections of regenerating RNC at (A) 2, (B) 6, (C) 12, and (E) 28 days post injury (dpi) were labeled with anti-GFS (green) and anti-BrdU (red). Animals that had undergone a transection of their radial nerve were injected with BrdU 24 hrs prior to sacrifice. (B) GFS expressing fibers can be seen to elongate out of the nerve stump by 6 dpi (arrow). (D) Restoration of GFS-expressing fibers in the radial nerve cord is complete by 28 dpi. In terms of cell division, little cell division is observed at (A) 2 or (D) 28 dpi. Actively dividing cells were mainly observed in the periphery of the RNC where most of the nuclei are present (arrows). Some cell division is also observed among cells in the neuropile. Cell division begins around (B) 6 dpi and peaks around (C) 12 dpi in both hyponeural and ectoneural components (arrows). EN-epineural component, HN-hyponeural component, RNC-radial nerve cord. X's denote the injury site; arrows signal some of the BrdU-labeled cells within the RNC. Bar = 300 μm.