Age-Related Changes in the Immunohistochemical Localization of Inducible Nitric Oxide Synthase (iNOS) and Nuclear Factor-kappa B (NF-κB) in the Mouse Cochlea

Localization of iNOS and NF-κB in the cochlear tissues of ddy-strain mice was studied immunohistochemically with reference to ageing. Severe structural disorders with a decrease in the number of cells were found, especially in the organ of Corti and in the spiral ganglion of older mice. Throughout all age-spans studied, iNOS-like immunoreactivity was found in the cells of Hensen, Claudius and the outer spiral sulcus epithelium, and it increased dramatically with age. A very small number of cells in the stroma of the spiral ligament and spiral limbus of younger mice up to 12 months of age showed weak iNOS immunoreactivity, while the spiral ganglion cells of the younger mice were almost negative. In mice after 18 months of age, however, strong iNOS immunoreactive cells remarkably increased in the spiral ligament and spiral limbus. Moreover, spiral ganglion neurons that survived from age-related cell death also showed strong reactivity. The immunohistochemical localization of NF-κB and its change with age were nearly the same as those of iNOS. The possible roles of iNOS and NF-κB in the changes of mouse cochlear tissues with advancing age were discussed.