Loss of retinal function in aged DBA/2J mice - New insights into retinal neurodegeneration.

The DBA/2J mouse is a common animal model of glaucoma. The intraocular pressure increases with age, and retinal ganglion cells (RGC) degenerate, usually starting at an age of approximately six months. In this study, we used two-year-old DBA/2J mice presuming an end-point of RGC degeneration. We investigated visual function in these animals using electroretinography (ERG) and visual evoked potentials (VEP), and we checked the number of remaining RGC by retrograde staining. Almost no RGC were left in the retina, and VEP were hardly recordable. Surprisingly, also ERG amplitudes of scotopic a-waves and b-waves, photopic b-waves and oscillatory potentials were decreased significantly by approximately 40% compared to amplitudes measured in age-matched C57BL/6J mice. The latencies were not changed in DBA/2J mice compared to C57BL/6J mice, and so were the ratios between amplitudes of a-waves, b-waves and oscillatory potentials. Our results indicate that, in addition to degeneration of RGC, also photoreceptors are affected by pathological processes in the eye caused by the mutations present in DBA/2J mice.