Figure 10. Pathology of the sciatic nerve and nerve terminals in the skin after spinal nerve injection.

(A) The diagram illustrates the peripheral processes and terminals of dorsal root ganglia (DRG) neurons. The peripheral processes typically degenerate after sciatic nerve transection (axotomy group) and spinal nerve crush (crush group) but remained intact after intra-DRG injection (intra-DRG injection group) and spinal nerve injection (spinal nerve injection group). (B–I) Sciatic nerves at the gluteal level were processed for nerve pathologic studies after axotomy, spinal nerve crush, intra-DRG injection, and spinal nerve injection. Axonal degeneration was prominent in the axotomy group and the crush group but not in the intra-DRG injection group and the spinal nerve injection group. (J–Q) The nerve terminals of the DRG neurons in the dermis of the skin from both groups were immunostained with anti-protein gene product 9.5 (PGP9.5), a pan-neuronal marker. In the skin on the contralateral hindpaw of the axotomy group and the crush group, PGP9.5(+) nerve fibers exhibited intense linear profiles forming interlacing networks; the dermal nerve fibers degenerated on the ipsilateral skin (J–M). In the intra-DRG injection group and the spinal nerve injection group, PGP9.5(+) dermal nerve fibers appeared with similar abundance on the ipsilateral and contralateral sides (N–Q). (R) The graph compares the dermal nerve fiber in the axotomy, crush, intra-DRG injection and spinal nerve injection groups. Bar, 10 μm (B–I), 25 μm (J–Q). *Statistically significant at p < 0.05.