Morphology of the cochlear nerve in Sprague-Dawley and brown Norway rats

Cochlear nerve morphology was studied in young adult albino (Sprague-Dawley) and pigmented (Brown Norway) rats. Analysis of the material included counts of normal and degenerating fibers and of glial cell nuclei, and measurements of vascularity and of the nerves' cross-sectional areas. The median number of normal fibers in the Sprague-Dawley rats was 21,216, and, in the Brown Norway rats, it was 20,186. There were no statistically significant differences between the two strains in numbers of normal fibers, degenerating myelin sheaths, or glial cell nuclei, or in the cross-sectional areas of the nerves. The area density of blood vessels was significantly higher in nerves from the Sprague-Dawley rats. The median area density in that strain was 0.0149, while in the Brown Norway rats the median area density was 0.0105.