Fig. 8.  In situ  hybridization (ISH) for nerve growth factor (NGF) messenger RNA (mRNA) in incised plantar skin and flexor digitorum brevis muscle. Sections are counterstained with fast red for nuclei. (  A ) ISH for NGF mRNA with the antisense probe 2 h after incision. (  B–H ) Higher-magnification photographs show NGF mRNA expression within epidermis and dermis (  B ), dense connective tissue in subcutaneous region (  C ), perimysium (  D ), perivascular connective tissue (  E ) and large nerve bundle (  F ) in deep tissue layer. (  G ) ISH in subcutaneous region adjacent to skin incision. (  H ) Flexor muscle fibers adjacent to muscle incision. (  I ) ISH for NGF mRNA with sense probe at 2 h after incision showing no positive staining. The  arrows indicate the incision. PO = postoperative.