Spongiform degeneration of the gerbil cochlear nucleus: an ultrastructural and immunohistochemical evaluation.

Observations from ultrastructural and immunohistochemical studies suggest that spongiform lesions in the gerbil cochlear nucleus are derived principally from dendrites. Almost one-fifth of the lesion profiles examined ultrastructurally exhibited synaptic contacts with axon terminals. In addition, approximately 80% of lesions are immunopositive for the dendrite-specific microtubule associated protein, MAP2. Ultrastructural studies showed a small percentage (8%) of lesions were derived from myelinated axons, although none were immunohistochemically labelled with antibodies to the tau protein. Staining with the astrocyte-specific markers GFAP, S-100 and vimentin yielded equivocal results, but did not support a major role for astrocytes in lesion formation. The histological profile matches that seen in some other well characterized types of spongiform degeneration.