Pigmented cells of the stria vascularis and spiral ligament of the chinchilla

This study was designed to investigate the cellular distribution and ultrastructure of melanin pigment in the stria vascularis and spiral ligament of the chinchilla cochlea. Typical dendritic melanocytes containing homogeneously distributed eumelanin granules were observed in the spiral ligament. In the stria vascularis melanin was found to occur in three types of cells (heavily pigmented cells that appear to be melanocytes, intermediate cells and basal cells). The melanocyte-like cells contain pigment globules composed of melanin granules, granular matrix and occasional lipid droplets in a configuration similar to that of neuromelanin. These cells are morphologically distinct from intermediate cells which contain sparsely distributed, small, dense granules apparently composed of melanin. The intermediate cells show a positive DOPA reaction and portions of the intermediate cell GERL system display intense acid phosphatase reactivity. The basal cells of the chinchilla stria were also found to contain occasional clusters of melanin granules. It is hypothesized that the basal cells may acquire melanin by donation from the other pigmented cells of the lateral cochlear wall.