Abstract
Purpose: :
We have succeeded in generating a rhodopsin Pro347Leu transgenic (Tg) rabbit, a model of retinal degeneration (Kondo M et al. IOVS, 2009). The purpose of this study was to characterize the pattern of the local retinal function during the course of retinal degeneration in Tg rabbits using focal ERGs.
Methods: :
Focal ERGs were recorded from 3-, 6-, and 12-month-old wild-type (WT) and Tg rabbits. A 15 degrees stimulus spot was used to elicit the focal cone ERGs from five different retinal areas, central, upper, lower, nasal, and temporal retinal areas. The amplitudes of the b-wave and the sum of the OPs in the five areas were compared.
Results: :
The amplitude of the b-wave and OPs of the focal ERGs of Tg rabbits decreased progressively with age at all 5 retinal areas. The amplitudes of the b-waves were not significantly different in the 5 recording sites. The amplitude of b-wave was 1.0-1.2 µV at 3 months of age, 0.6-0.7 µV at 6 months, and almost non-recordable at 12-months.The amplitude of the b-wave of the wild rabbit was 2.3-3.1µV.Interestingly, the summed OP amplitudes of the Tg rabbits varied in the different regions, and the amplitude of the upper area (1.1 µV) was significantly larger than other parts (0.4-0.6 µV) at 3 months of age. The amplitudes of the OPs were also reduced at 6 months but the regional variation remained.
Conclusions: :
The amplitudes of the b-wave in Tg rabbit, which originate mainly from bipolar cells, progressively decrease with increasing age but there were no regional differences. The OPs, on the other hand, were significantly larger at the upper area of the retina. These findings indicated that during the course of retinal degeneration, the retinal cone function does not degenerate equally in different regions. Because the OPs are presumed to originate from inner retinal neurons, especially from the amacline and/or ganglion cells, our results suggest that the secondary changes of these cells after photoreceptor degeneration are not uniform.
Keywords: electroretinography: non-clinical • retinal degenerations: hereditary • electrophysiology: non-clinical