Abstract
Purpose: :
The retinal degeneration 6 (rd6) mouse has a retinal phenotype resembling clinical human retinitis punctata albescens. White spots detected by fundus examination appear across the retina at 8 to 10 weeks of age and persist through to the advanced stage of retinal degeneration. Histologically, the spots appear in the subretinal space, between the photoreceptors and retinal pigment epithelium (RPE). Photoreceptor cells progressively degenerate with age and abnormal electroretinograms (ERGs) are seen from about 1 month of age. We have previously reported that ERG c-waves can be recorded noninvasively using contact lens electrodes with built-in high intensity white light-emitting diodes and an alternating current amplifier (2007, ARVO). The same electrodes and amplifier were used for recording full-field conventional ERGs in a mouse model of RPE degeneration (2007, ARVO). The purpose of the present study was to analyze the time course of the c-waves of rd6 mice using the same electrodes and amplifier in order to elucidate the association between RPE function and retinal dysfunction in rd6 mouse.
Methods: :
The c-waves were recorded from rd6 mice (n=10) once every 2 weeks from 4 to 70 weeks of age. The c-waves were also recorded from wild type (w/t) C57BL/6 mice (n=10) as a normal control. The c/b ratios and implicit times were analyzed.
Results: :
The c/b ratios of rd6 mice were significantly lower than that of w/t-C57BL/6 mice throughout the observation period; however, there was no significant difference in implicit time between the two groups. In comparison within the rd6 mice group, the c/b ratios gradually decreased with age and were significantly lower at 30 weeks than that at 4 weeks. The implicit time elongated significantly at 6 weeks than that at 4 weeks.
Conclusions: :
C-wave amplitude is significantly lower in rd6 mice compared with normal C57BL/6 mice, from 4 weeks. The amplitude also decreases gradually with age. These findings indicate that dysfunction or degeneration of retinal pigment epithelium may be one of the causes of retinal degeneration in rd6 mice.
Keywords: electroretinography: non-clinical • retinal pigment epithelium • retinal degenerations: hereditary