[Histochemical study of retrograde degeneration in ligated peripheral nerves]

The enzyme specificity of the Karnovsky staining was examined. Tetraisopropylpyrophosphoramide made the staining difference between anterior and posterior roots clearer. Rat sciatic nerve, gluteal muscle branch and sural nerve were ligated and retrograde changes were examined histologically and histochemically. In ligated sciatic nerve, axonal degeneration similar to Wallerian degeneration occurred within 5 mm proximal to ligation while acetylcholinesterase activity decreased in more proximal portions. Sections of ligated gluteal muscle branch showed marked increase of small myelinated fibers 6 weeks after ligation and the mean cross sectional area of myelinated fibers decreased due to the new small fibers. The mean cross sectional area of myelinated axons also decreased in ligated sural nerve but myelinated fibers did not so remarkably increase in number as ligated gluteal muscle branches. Histochemical funicular orientation could be reliable if performed soon after nerve injury before retrograde changes spread in the proximal stump.