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SA Nirenberg, AL Jacobs, JR Sinclair; Using Targeted Cell Class Ablation to Dissect Circuits in the Inner Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):897.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The inner retina contains a complex class of interneurons, the amacrine cells. These cells fall into distinct groups, whose functions have been difficult to reveal. Here we used a targeted ablation method to study the role of one such group, a set of GABAergic amacrine cells that co-express neuropeptide Y (NPY/GABA cells). Our aim was to determine how ablation of these cells would affect ganglion cell responses. Methods: NPY/GABA cells were ablated from mouse retinas using an eyecup preparation, and ganglion cell responses to several stimuli (checkerboards, flashes, drifting gratings) were recorded extracellularly. Results: Ablation of the NPY/GABA cells had little effect on temporal integration, but a strong effect on spatial integration. Ganglion cells from retinas depleted of NPY/GABA cells showed a change in their spatial frequency tuning, a shift toward higher frequencies (P<0.01, Student's t-test). The shift was dose dependent: retinas with a greater loss of NPY/GABA cells showed a greater shift, with the highest reaching twice that of controls (P<0.01, regression test). To evaluate this shift in spatial frequency in the context of a receptive field model, we fit the spatial frequency profile of each ganglion cell to a difference of Gaussians model for center and surround. The model showed that the predominant effect of losing NPY/GABA cells was a reduction in the size of the surround. Conclusion: The working hypothesis for many years has been that amacrine cells are involved primarily in temporal and motion processing. Recent reports (e.g., see Cook and McReynolds,1998; Flores-Herr et al., 2001) suggest that they may play a key role in spatial processing as well. These studies show that perturbations of amacrine cell activity can alter basic center/surround organization. Our findings provide further support for this idea, and show that we have tapped into an inner retinal circuit involved in shaping surrounds.
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