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S. Bisti, S. Di Marco, V. Nguyen, R. Maccarone, D. A. Protti; Long-Term Morpho-Functional Retinal Modifications Induced by Dark-Rearing. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3841.
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The functional properties of retinal networks and the morphology of their constituent cells undergo remarkable changes during development and are subject to modifications by sensory experience. Visual deprivation at early developmental stages strongly alters functional and structural properties of retinal circuits in an apparently reversible manner. We have recently shown, however, that long-term dark-rearing permanently modifies the spontaneous synaptic inputs to retinal ganglion cells (RGCs). In order to determine if dark-rearing induces permanent changes in the organisation of retinal networks, we characterized its effects on the receptive field (RF) properties of RGCs and on the morphology of some retinal cell types at different times following a return to normal light conditions.
Rats were born and raised in complete darkness for 1-3 months and returned to normal circadian rhythm for at least 2-6 months (recovery). Rats of matching age were used as controls. Retinas were dissected and maintained in carboxygenated Ames medium under infrared illumination. Light-evoked responses elicited with spots of different diameters, annuli and/or sinusoidal gratings were recorded from RGCs in whole-mount retinas from control and dark-reared rats either in voltage-clamp mode to investigate the properties of direct inhibitory and excitatory inputs onto RGCs, or in current-clamp mode to investigate their spiking behaviour and subthreshold membrane fluctuations.
The receptive field centre of RGCs in dark reared/recovery animals was smaller and the strength of the antagonistic surround was increased compared to controls. Moreover, most of the RGCs in dark-reared/recovery animals seemed to display increased inhibitory input and RFs not organised in a classical concentrical manner. At the morphological level, retinas of treated animals showed changes in bipolar cells and RGCs and a significant reorganization in the cholinergic amacrine cells mosaic.
Our data suggests that visual deprivation induces long-term changes in retinal structure and function.
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