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R. Weiler, M. Pottek, M. Seeliger, P. Humphries; Dynamics of Horizontal Cell Coupling in Wild Type and Rhodopsin Knockout Mouse Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4174.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The mouse has become a favored subject in retinal research due to transgenic techniques, but little is known about the physiological properties of retinal cells and pathways. We therefore analyzed the light-dependent characteristics of the horizontal cell network. Methods: Intracellular recordings combined with injection of the tracer Neurobiotin were performed in everted and superfused eyecup preparations. Results: Horizontal cells displayed a dark potential of –30 to –40 mV and typical hyperpolarizing light responses with amplitudes of maximally 20 mV. Sensitivity was substantial in the blue and green part of the spectrum, but only poor with longer wavelength stimulation. Responsiveness declined following light adaptation and recovered during several minutes of dark adaptation. Tracer injection into a soma resulted in an intense spread among the neighboring somata. Tracer coupling was largest in a short-term dark adapted and light sensitized condition (553 somata ± 212 S.D.; n=4) and was greatly attenuated following prolonged darkness (195 ± 56; n=4) or extended light adaptation (178 ± 46; n=4). These triphasic dynamics were also observed for the tracer coupling of injected axon terminal arborizations. In general, coupling between the axon terminals was considerably smaller than for the somata. The tracer diffused more or less radially over about 120 µm from the injection site, which is only half the value for the spread in the somatic network after prolonged darkness or light adaptation. Terminal coupling was absent following prolonged dark adaptation or light adaptation. Horizontal cell coupling was also examined in rhodopsin knockout mice in which light sensitivity is mediated exclusively by cones. The general dynamics were similar to the wild type mice, with intense somatic coupling following short-term dark adaptation (650 ± 22; n=3) and reduced tracer spread after prolonged darkness (360 ± 65; n=3) or light adaptation (184 ± 48; n=3). Conclusion: Light responsiveness and gap junctional communication of horizontal cells depend strongly on the ambient light conditions in both the wild type and the rhodopsin knockout mouse, suggesting a prominent role of the cone pathway.
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