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C. E. Strang, K. E. Gavrikov, K. T. Keyser; Activation of Upstream Nicotinic Acetylcholine Receptors Affects Ganglion Cell Response Properties. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1864.
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Cholinergic modulation of retinal ganglion cell response properties takes place at the level of the inner plexiform layer (IPL) and is mediated by interactions of nAChRs expressed by ganglion cells and upstream cells. Immunohistochemical and physiological evidence suggests that subsets of glycinergic and GABAergic amacrine cells express alpha7 and/or non-alpha7 nAChRs and that cholinoceptive amacrine cells can provide inhibitory feedback to one another as well as to retinal ganglion cells. As a result, cholinergic agents, acting on cholinoceptive amacrine cells, can affect light-evoked currents and center surround organization of retinal ganglion cells with concentric receptive fields.
Rabbit retina slices and eyecups were used for whole cell patch clamp recordings to test the modulation of amacrine and ganglion cell responses by cholinergic agonists and antagonists. Whole cell configuration was obtained under visual control and cell morphology was confirmed with fluorescent dye injection. Amacrine and ganglion cell responses to cholinergic agents were tested and ganglion cell receptive field center and surround responses were tested before and after cholinergic blockade.
The responses of probable amacrine cells in the innermost 1 or 2 tiers of cells in the INL to application of nicotine and or choline were recorded. Inward currents were blocked or reduced by methyllycaconitine (MLA) and/or hexamethonium bromide. Outward currents that were sensitive to cholinergic antagonists were also observed in subsets of amacrine cells. Cholinergic blockade affected ganglion cell currents evoked by full field, spot, or annular light stimulation, and in some cases differentially affected the center and surround responses.
These data indicate that more than one nAChR subtype may play a role in the modulation of ganglion cell responses by amacrine cells. These data indicate that rabbit retinal ganglion cell response properties are directly and indirectly affected by cholinergic input and suggest a role for cholinergic modulation of center surround receptive field organization.
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