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D.K. Merwine, E. Lee, L.B. Mann, N.M. Grzywacz; Alteration of Retinal Cholinergic Circuitry by Dark Rearing . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4023.
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Purpose: Visual deprivation alters retinal ganglion cell (RGC) synaptic inputs. For instance, in dark–reared turtle retina, areas of RGC receptive fields are twice as large as in control retinas (Sernagor & Grzywacz, 1996). One hypothesis for these changes is that dark rearing induces modifications in the activity of specific classes of amacrine cells. In this study, we evaluated whether visual deprivation influence the network of cholinergic amacrine cells in the inner retina. Methods: We used turtle retina’s immunocytochemistry against choline acetyltransferase (ChAT). Control turtles were maintained in a regular 12–hour light/dark cycle from hatching. Light–deprived turtle retinas were obtained by rearing animals in total darkness. Results: As in other studies, in control retinas, ChAT immunoreactivity was localized to INL and GCL cells, with dendrites in Strata 2 and 4 of the IPL respectively. The same happened in dark–reared retinas, but for them, the density of detectable ChAT–immunoreactive cells in both the INL and GCL was significantly higher. At some eccentricities, this density was 40% higher than in control animals. Near–neighbor analysis revealed that the denser population of cholinergic cells in dark–reared turtles formed a mosaic as regular as the normal ones. Conclusions: These results indicate that changes in the expression of neurotransmitter in some kinds of amacrine cells may underlie some of the effects that dark rearing has on retinal–ganglion–cell receptive fields. The high regularity of control and dark–reared mosaics, suggest that repulsion mechanisms controlling the relative position of turtle amacrine cells still function after hatching.
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