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Marianna Bacellar-Galdino, John Rozofsky, Simon M Petersen-Jones, Jeffrey Adam Jamison; Light and Dark discrimination testing in Gnb3-/- rats. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4280.
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© ARVO (1962-2015); The Authors (2016-present)
The Acuisee-R device is a specialized operant chamber designed to automatically train and measure the threshold of discrimination between two target stimuli. Previously we demonstrated measurement of visual acuity and contrast sensitivity in Long Evans rats (Bacellar-Galdino et.al., 2018). However, in animals with advanced retinal degeneration or with poor acuity, such as albino animals, the device can be used to measure the threshold of light vs dark discrimination.Gnb3 codes for Gβ3 which plays an important role in ON bipolar cell signaling. Gnb3-/- albino rats are therefore a model for CSNB. They have very reduced rod bipolar cell function and a no b-wave dark-adapted ERG. However their cone ERG is relatively normal as is the rod a-wave. The purpose of this study was to demonstrate the ability to train normal and Gnb3-/- albino animals to discriminate between bright vs dark targets under photopic conditions and measure the threshold of luminance discrimination under photopic and scotopic conditions.
Using the AcuiSee-R device, ten ss Dahl rats (5 wild-type / 5 Gnb3-/-) were trained to discriminate between a white and a dark target. They were tested under light adapted conditions (0.16 log cd/m2) and 4 background lights inside the box (-1.2, -2.1, -2.6 and -3 log cd/m2) following 12 hour dark adaption. Neutral density filters were applied to the tablet in order to reduce light output. The threshold of discrimination was evaluated 4x per animal under each condition.
Eight (5 wildtype and 3 Gnb3-/-) out of the ten rats could be trained to the task under light adapted conditions. WT albino rats could be trained within 7-9 sessions and Gnb3-/-rats within 12. Considering the brightest image 1 and the darkest 0, no statistical significance was observed between groups under 0.16, -1.2 and -2.1 log cd/m2 background luminance. At -2.6 and -3 log cd/m2, Gnb3-/- rats had a significant decrease in image discrimination threshold, 0.41±5.3 and 0.53±2.2; and 0.28±2.72 and 0.52±2 Gnb3-/- and albino respectively (ANOVA, p=0.02 and p=0.007).
This work demonstrates that albino rats can be trained to the simplified visual task of light dark discrimination and that Gnb3-/- rats have reduced light/dark discrimination compared to wild-type rats under dim lighting conditions.
This is a 2020 ARVO Annual Meeting abstract.
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