The distribution of peroxidases in the sciatic nerves of normal and hexachlorophene intoxicated developing rats

Horseradish peroxidase (mol. wt. 40 000) or microperoxidase (mol. wt. 1900) were injected over the sciatic nerve of normal or hexachlorophene (HCP) intoxicated developing rats (3,7,14 and 21 days). Light and electron microscopic studies of nerves after histochemical staining for peroxidase revealed: a) the perineurial barrier to the two peroxidases was established in 21 day normal and HCP intoxicated rats; b) in animals 3-14 days, the perineurial barrier to both peroxidases was not formed and peroxidase staining was observed in the periaxonal space and in the space between paranodal loops of myelin; c) intramyelinic vacuoles, induced by HCP in animals 7-14 days did not show peroxidase staining. HCP-induced intramyelinic vacuolation is due to the separation of the myelin lamellae at the intraperiod line; although these vacuoles are potential extensions of the extracellular space, they are not stained with the extracellular markers horseradish or microperoxidase.