Phosphotungstic acid staining of the organ of corti for electron microscopy

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Abstract
Phosphotungstic acid (PTA) 1% in absolute alcohol was used, according to Bloom and Aghajanian's ('66) method, during the final dehydration stage of glutaraldehyde‐fixed cochlear specimens which were processed for electron microscopic study without osmium treatment. Familiar structures emerged with additional characteristics. PTA stained supporting elements. Synaptic areas were emphasized and the synaptic bar of hair cells opposite afferent endings was densely stained. Dark clumps were found near the synaptic surface of efferent nerve endings that seemed to correspond to the material sometimes seen between vesicles near the synaptic cleft. A dense layer was present in hair cells opposite efferent terminals between the outer layer of the double membrane and the synaptic membrane. Formations resembling synapses between the nerve endings of outer hair cells were emphasized by PTA staining, but were difficult to find because of their rarity. It seems unlikely that synaptic interaction between cochlear nerve endings is vital in the basic physiology of hearing.PTA staining permits recognition of cochlear nerve ending type independent of hair cell features which will make it a useful aid for the study of the development of the inner ear and of pathological ear conditions.