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MT Schiavone, NS Peachey; Influence of Rods on Adaptation-Induced Changes in the Mouse Cone ERG . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1840.
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Purpose: The response properties of mouse cone electroretinograms (ERGs), isolated by superimposing flashes upon a steady adapting field, change during the first minutes of light adaptation . To determine the role of rods in this process, we tested transducin null (Tr-/-) mice in which rods are anatomically normal but do not respond to light . Methods: Mice were bred to generate Tr-/- and Tr+/- littermates. After overnight dark adaptation, mice were anesthetized (ketamine/xylazine) and placed on a heating pad. Responses were recorded first in the dark and then as a function of time following the presentation of a steady adapting field (1.5 log cd/m2). Results: In response to a dim flash (-2.6 log cd sec/m2) presented to the dark-adapted eye, ERGs of Tr-/- mice were flat whereas those of Tr+/- mice were normal, as previously noted . Cone ERGs were obtained from both Tr+/- and Tr-/- mice in response to high-intensity flashes (1.9 log cd sec/m2) superimposed on the adapting field. In Tr+/- mice the cone ERG b-wave gradually doubled in amplitude, and became faster as light adaptation proceeded. In contrast, any changes observed in Tr-/- mice were of much smaller magnitude. Aside from these differences, cone ERGs recorded at the end of light adaptation were comparable in amplitude and timing. Similar results were obtained when the OP wavelets were examined individually. Conclusion: In the mouse eye, the process that underlies the adaptation-induced changes of the cone ERG is influenced by rod activity. This is different from the human eye, wherein these adaptation-induced changes appear to be intrinsic to the cone system. Peachey et al. (1993) Neurosci Lett 162: 9-11. Calvert et al. (2000) Proc Natl Acad Sci USA 97: 13913-8.
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