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H. Fong, L. Rife; Heterogeneity of RGR knockout mice in response to 10–Hz flicker cone ERG . Invest. Ophthalmol. Vis. Sci. 2004;45(13):822.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Light–adapted RGR knockout mice show a low–amplitude cone ERG response compared to normal mice. The goal of this work is to continue study of the cone ERG response in mice that lack the RGR opsin. Methods: Baseline ERGs were recorded from dark–adapted mice. Mice were also pre–adapted for various times under constant fluorescent lighting at 70 foot–candles (fc) before the measurement of cone ERG b–wave amplitudes. The cones were stimulated with a single bright flash or 10–Hz flickering via a Grass xenon flash at full intensity. To isolate the cone ERG response, a rod–desensitizing background field at 6 fc was applied throughout the period of stimuli presentation. In this study, one of two independent lines of RGR knockout mice was used (R1). Results: b–Wave amplitudes in response to 10–Hz flicker stimuli were recorded from dark–adapted RGR–/– and RGR+/+ mice (no pre–adaptation). A subset of RGR–/– mice showed no difference in magnitude of response compared to wildtype mice. Other dark–adapted RGR–/– littermates had lower cone ERG b–wave amplitudes from the 10–Hz flicker stimuli. When the mice were retested, a significant majority of dark–adapted RGR–/– mice that had a low or normal response showed reproducible low or normal b–wave amplitudes again. The difference in b–waves of the low–amplitude mice was significant. When the mice were pre–adapted 1–4 hr under constant light, cone ERG b–wave amplitudes from 10–Hz flicker stimuli were significantly lower in all RGR–/– mice compared to RGR+/+ controls. Conclusions: A subset of RGR–/– mice has a low–amplitude cone ERG response even without pre–adaptation to light. These differences in behavior are revealed in RGR knockout mice and may be due to an underlying genetic heterogeneity.
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