Abstract
Abstract: :
Purpose: The retinal degeneration 6 (rd6) mice is a new, animal model with slow retinal degeneration that is associated with distinctive white dots or flecks in the retina (Hawes et al., 2000). The mutation developed spontaneously, but the causative gene has not been identified. rd6 is thought to be a mouse model of human retinitis punctata albescens. The purpose of this study was to investigate the electrophysiological changes in the early stages of the retinal degeneration in rd6 mice. Methods:Full-field ERGs were recorded from 8-32 week old rd6 mice. Scotopic and photopic intensity-response curves from rd6 mice were compared to those from control mice. The temporal course of dark-adaptation was followed by recording ERG rod responses after intense bleaching. Results: At 8 weeks, the amplitudes of the scotopic a- and b-waves of the rd6 mice were reduced: a-waves, 50% of the control; and b-waves, 70% to the control. However, the photopic ERG amplitudes were still within the normal range. Thereafter, both scotopic and photopic ERGs gradually declined with age. The b/a wave ratio was significantly large with in the rd6 mice. There was no significant difference in the recovery rate of rod responses after intense bleaching. Conclusion: rd6 mice showed a slow retinal degeneration with initial normal cone function. The relatively better preserved b-wave than the a-wave in rd6 mice has been reported in other animal model of retinal degeneration (Machida et al., 2000; Cideciyan et al., 2001, etc.), and may be related to the buffering effect of the rod bipolar cells against the loss of photoreceptors or a compensatory postreceptoral mechanism.
Keywords: 396 electroretinography: non-clinical • 316 animal model • 562 retinal degenerations: hereditary