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Ye Long, Konstantin E. Gavrikov, Christianne E. Strang, Kent T. Keyser; Cholinergic Modulation Affects Light Responses And Receptive Field Organization Of Ganglion Cell Subtypes. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4581.
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© ARVO (1962-2015); The Authors (2016-present)
Acetylcholine receptors (AChRs) are extensively expressed by bipolar, amacrine, and ganglion cells in retina. Nicotinic and muscarinic AChRs expression by retinal ganglion cells has been shown by RT-PCR, immunohistochemistry, and electrophysiology. However, the balance between nicotinic and muscarinic cholinergic modulation of ganglion cell response properties is still unclear. This study demonstrates that cholinergic modulation by multiple AChRs affects center-surround receptive field organization and other response properties of ganglion cells.
Rabbit eyecups were used for whole cell patch clamp recordings to test effects of cholinergic agents on ganglion cell light responses. Cell morphology was confirmed by injecting Lucifer Yellow (1-1.5mg/ml). Different sizes of light spots and annuli were used to characterize the receptive field. Moving light bars were used to identify direction and orientation selectivity of complex ganglion cells. Light responses were recorded before and after the application of the nicotinic antagonists methyllycaconitine (MLA: 100nM) and hexamethonium bromide (HEX: 100µM) and/or the muscarinic antagonist atropine (ATR: 3µM). After recording, eyecups were fixed with 4% paraformaldehyde, mounted on slides and images of the cells were acquired using a Leica TCS 4D confocal microscope.
The data demonstrate that both nicotinic and muscarinic AChR activation modulates the light responses of retinal ganglion cells. The effects of blockade of nAChRs and/or mAChRs varied depending on cell type. The size of ganglion cell receptive field centers were reduced or enlarged by cholinergic antagonists. Confocal fluorescent images of filled ganglion cells provided confirmation of ganglion cell type.
The light responses of ganglion cells can be affected by both nicotinic and muscarinic AChR activation and blockade. The light response and receptive field organization of several types of ganglion cells were changed by the application of cholinergic antagonists and included effects on both center and surround responses. The responses may have been mediated by nAChR and/or mAChR activation on the ganglion cells themselves as well as on upstream amacrine and bipolar cells. The effects of cholinergic agents on subsets of ganglion cells are complex and require additional study.
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