Abstract
Purpose
Previous work has suggested that the retinal degeneration mutant rd8 mouse lacks an electroretinographic (ERG) phenotype until about 9 months of age. We evaluated the ERG phenotype of these mice by measuring both conventional ERG responses and scotopic threshold responses.
Methods
Groups of 4-month-old wild-type (WT) and mutant (rd8) mice were anesthetized and tested for mass retinal responses (ERGs) to several types of visual stimuli. Scotopic threshold responses were accumulated with brief scotopic flashes at a series of very dim intensities. Dark-adapted (scotopic) and light-adapted (photopic) responses to brief flashes at a series of higher intensities were recorded, along with long flashes and random modulations of light levels under photopic conditions.
Results
Negative scotopic threshold responses (nSTRs) had lower amplitudes in rd8 mice compared to WTs. Positive scotopic threshold responses were similar in the two groups. With the more intense stimuli, a- and c-wave amplitudes were smaller in rd8 mice. Both scotopic and photopic b-wave amplitudes tended to be larger in rd8 mice, though generally not significantly.
Conclusions
The striking decrease in nSTR amplitudes was surprising, given that the main retinal effects of the rd8 mutation occur in the outer retina, at the external limiting membrane. The primary source of nSTRs in mice is thought to be at the amacrine cell level in the inner retina. Investigation of how this mutation leads to inner retinal dysfunction might reveal unexpected aspects of retinal cell biology and circuitry.
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Funding
National Institutes of Health/National Eye Institute provided financial support in the form of grants 2R01EY012830, R01EY014560. The James and Jean Culver Vision Discovery Institute also provided financial support. The sponsors had no role in the design or conduct of this research.
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No human subjects were tested in the present study.
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All procedures were approved by the Institutional Animal Care and Use Committee of Augusta University, and followed the ARVO guidelines for the use of animals in ophthalmic and visual research.
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Saul, A.B., Cui, X., Markand, S. et al. Detailed electroretinographic findings in rd8 mice. Doc Ophthalmol 134, 195–203 (2017). https://doi.org/10.1007/s10633-017-9585-y
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DOI: https://doi.org/10.1007/s10633-017-9585-y