Fig. 4

Location of BHRP-labeled motoneurons and primary sensory afferent spinal projections. A–C Darkfield digital micrographs of transverse hemisections through lumbar spinal cord injection of Botulinum–toxin conjugated HorseRadish Proxidase (BHRP) in the tibialis anterior muscles. A BHRP injection into the TA muscle labeled control, undamaged, motoneurons in the L3 spinal segment in the contralateral side (Unoperated). BHRP injection into the ipsilateral TA after PEG-fusion repair of segmental-loss sciatic nerve PNI often labels original appropriate motoneurons in L3 segments A as well as atypical, inappropriate motoneurons in other spinal segments (B), e.g., L6 and sensory afferents (black arrows). C Anomalous sensory afferent terminal labeling in dorsal horn lamina I–V of L3 through L6 segments of PEG-fused Allograft animal at 17 days PO. Scale bar = 100 μm. D Polar plots of total length of dendritic material divided into radial sectors for measure of motoneuron dendritic distribution in 6 bins of 60° each. Bar lengths represent means ± SEM. * indicates significantly different from Unoperated Controls (p < 0.05). E Patterns of motoneuron and sensory labeling in spinal cord segments L3–L6 after injecting BHRP into the TA in PEG-fused Allograft animals. S: Sensory, M: Motor. Gray L3 M bar indicates normal location of TA motoneurons in Unoperated Controls. Blue open circles indicate location of sensory terminal label; filled circles indicate location of BHRP-labeled motoneurons. Vertical dashed lines represent labeling across multiple lumbar sections within individual animals sampled at a given PO time