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Michael Risner, Chad Jackson, Douglas McMahon; Dopamine differentially affects network light adaptation in ON- and OFF-center transient retinal ganglion cells. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3421.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal light adaptation involves at least two mechanisms: photoreceptor and network adaptation. Network adaptation involves the synapses between inner nuclear layer neurons and retinal ganglion cells (RGC). Network light adaptation is mediated in part by dopamine, which reconfigures retinal circuitry depending on the prevailing lighting condition. The purpose of this study was to examine how dopaminergic pathways influence network light adaptation in RGCs.
Using a transgenic mouse model in which retinal dopamine is depleted by selectively knocking out the tyrosine hydroxylase gene in the retina (rThKO), we assessed the effect of dopamine on network light adaptation in RGCs. Whole retinas from rThKO or WT mice were dissected under dark conditions and mounted onto a recording chamber and RGCs were targeted for loose patch recording. RGCs were physiologically defined by their response polarity and duration by flashing a square of light over the RGC body. Network light adaptation was assessed by presenting an increment (for ON-center cells) or decrement (for OFF-center cells) of light onto a photopic background. To measure network light adaptation in physiologically defined RGCs we analyzed the mean spike output produced by probe stimuli over time under background light.
Network light adaptation was assessed in four types of cells: ON- and OFF-center sustained and ON- and OFF-center transient RGCs. Preliminary results indicate that network light adaptation is not affected by knocking out retinal dopamine in ON- and OFF-center sustained RGCs. There was no significant difference between the network light adaptation profiles of WT and rThKO ON- and OFF-center sustained RGCs. However, network light adaptation was altered in rThKO ON- and OFF-center transient RGCs. Furthermore, the knocking out retinal dopamine differentially alters network light adaptation in ON- and OFF-center transient RGCs.
In conclusion, dopamine is directly involved during network light adaptation in ON- and OFF-center transient RGCs. We suspect this difference in network light adaptation in ON- and OFF-center transient RGCs may be due to the influence of distinct dopamine receptors.
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