Abstract
Purpose: :
We have generated a rhodopsin Pro347Leu transgenic (Tg) rabbit model of retinal degeneration, and have characterized the pattern of degeneration by histological methods. The purpose of this study was to analalyze the the pattern of cone degeneration electrophysiologically using focal and full-field ERGs.
Methods: :
ERGs were recorded from 4 pigmented Tg and 3 wild rabbits at 3- and 7-months-of-age. For the focal ERGs, an infrared fundus camera (Kowa, Nagoya, Japan) was modified to observe the fundus and stimulate focal areas of the retina. Focal ERGs were elicited by a 15 degree spot centered on the visual streak. The luminance of the white spot was 30 cd/m2 on a rod saturating background. For full-field photopic ERGs, animals were placed in a Ganzfeld bowl and stimulated with stroboscopic stimuli of 3 cd/s/m2 on a rod-suppressing white background.
Results: :
To confirm that our ERGs were focal, a 15 degree laser burn was made on pigmented wild-type rabbit retinas, and ERGs were recorded when the stimulus spot was placed on that area. ERGs were not detected when the stimulus spot was placed on the lasered area, while distinctive ERGs were recorded from normal areas of the retina. These results indicated that our system could record focal ERGs from rabbit retinas. The amplitude of the focal ERGs b-wave from wild rabbit was 2.2- 3.4 µV, while that of Tg rabbit was <1.2 µV at 3 months and non-recordable at 7 months. The amplitude of full-field photopic ERG b-wave for wild rabbit was 105-132 µV, and that of Tg rabbit remained 32-61 µV even at 7-months-of-age.
Conclusions: :
We have successfully recorded focal ERGs from rabbit retinas. A comparison of the focal and full-field ERGs of Tg rabbit suggests that the loss of photoreceptors in the central retinal area was more severe than that in the peripheral retina. These results are comparable with our histological results.
Keywords: electroretinography: non-clinical • retinal degenerations: cell biology • retina