Selective staining by the fluorochrome 5,5-diphenyl-9-ethyl-oxacarbocyanine. II. Application to paraffin embedded nervous tissue.

We present a simple and rapid method to label specific structures of neural tissue in paraffin sections. After incubation of deparaffinized sections in the cyanine dye 5,5'-diphenyl-9-ethyl-oxacarbocyanine (DEOC), three different washing and mounting procedures were performed. Incubation in DEOC followed by washes in ethanol and water and mounting in glycerol-gelatin resulted in selective labeling of myelin in the central and peripheral nervous systems. Weak labeling of myelin and axons and staining of nuclei of neurons was seen after incubation in DEOC followed by washes in ethanol and xylene, and mounting in Eukitt. Nuclear proteins, the endoplasmic reticulum and the Golgi apparatus were stained strongly and exclusively after incubation in DEOC, washes in water, ethanol and xylene, and mounting in Eukitt. Thus the absorption pattern of DEOC is changed significantly by solvents applied after the fluorochrome. In any case, fluorescence did not fade even after repeated and intense fluorescence microscopy over a period of 6 months.