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We performed an immunohistochemical investigation of the distribution of glucocorticoid receptors (GRs) in the murine inner ear and found that GRs were expressed extensively, but with various degrees of immunoreactivity in different regions. We observed the strongest GR expression in the type III fibrocytes of the spiral ligament. Although the immunoreactivity of the cochlear hair cells and of the vestibular sensory epithelia was weak, the neighboring cochlear supporting cells and the subepithelial regions of the vestibular sensory epithelia were immunostained. Staining for GRs was also positive in the spiral ganglia and vestibular ganglia, as well as in the endolymphatic sac. The role of GRs in the inner ear is discussed.

Cytokeratin expression in the vestibular labyrinth of the guinea pig was investigated with immunofluorescence and immunoperoxidase staining on surface preparations of the vestibular epithelium. Phalloidin, an F-actin-specific probe, was used to distinguish between hair cells and supporting cells. Cytokeratin expression was not found in the cytoplasmic domain of hair cells of the crista ampullaris, utricle, or saccule. Cytokeratin expression was abundant in supporting cells of the vestibular sensory epithelium. Electron microscopy revealed the presence of desmosomes, which are associated with cytokeratins, within type 2 hair cells of the vestibular epithelium. It appears that cytokeratins are absent within the cytoplasmic domain of hair cells, but are present in association with intercellular junctions. The functional significance of this unique pattern of cytokeratin expression within the vestibular epithelium is discussed.