Diaminobenzidine as a myelin stain in semithin plastic sections

A diaminobenzidine (DAB) stain for myelin in glutaraldehyde fixed, osmicated, semithin epoxy sections is described. One or 1.5 mu m sections, dried onto slides, are first etched with a 1:2 dilution of saturated sodium ethoxide:absolute ethanol, then incubated in 0.05% aqueous DAB with 0.01% hydrogen peroxide, DAB specifically stains osmium fixed myelinated nerve fibers. This permits high resolution light microscopic study of myelinated nerve fibers in semithin sections of tissues that also can be studied by electron microscopy.