Age‐Related Changes in the Mouse Outer Retina

Purpose. To define the physiological and structural changes that may accompany aging in the normal mouse retina. Methods. C57BL/6 mice were maintained under cyclic light for either 2, 6, or 12 months. After rod‐ and cone‐mediated corneal electroretinograms (ERG's) were recorded from anesthetized animals, the retinal structure was quantitatively examined. Photoreceptor cell density was measured within 100‐μm regions of the central superior and inferior retina. Cone photoreceptor subtypes were identified by immunocytochemistry. Results. The amplitudes of rod‐ and cone‐mediated ERG's were reduced in older mice, although the overall ERG wave‐form did not change appreciably and implicit times were not changed in an age‐dependent fashion. In comparison, there was no significant age‐related decline in rod or cone photoreceptor density. Conclusions. The amplitude of the mouse ERG declines with age. This change does not appear to reflect a change in the structural integrity of the photoreceptor cells. In functional studies of murine models of late‐onset retinal disorders, it will be important to take these changes into consideration.