Alcian blue staining of cochlear hair cell stereocilia and other cochlear tissues

Using whole-mount surface preparations of the chinchilla organ of Corti, the anionic characteristics of cochlear tissues was investigated with the polycationic dye Alcian Blue. Our primary goal was to specifically stain the hair cell stereocilia for the purpose of producing cytocochleograms. To specifically stain hair cell stereocilia we investigated the effects of different fixatives and the 'critical electrolyte concentration' [Scott and Dorling (1965) Histochemie 5, 221-233] of MgCl2 on staining specificity. The stereocilia and the tectorial membrane were the most intensely stained cochlear structures and presumably have a strong negative charge. The most important factor in producing specific staining was fixation in osmium tetroxide rather than the addition of an electrolyte to the Alcian Blue staining solution. The use of Alcian Blue produced intense staining of hair cell stereocilia against an unstained background using standard, brightfield light microscopy.