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HE Kolb, E de Juan, A Angulo, N Cuenca; Two Types of Cholineacetyl Transferase-IR Amacrine Cells are Found in the Vertebrate Retina . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2779.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Acetylcholine (ACh) is commonly associated with "starburst" amacrine cells in the vertebrate retina. This mirror-symmetric pair of cells is involved in laying down the architecture of the IPL during development and in circuitry underlying directional selectivity. A second type of ACh-containing cell type has been described in some retinas. We sought further for such ACh2 cell types in other vertebrate retinas. Methods:Wholemount and cryostat retinas of different species (salamander, turtle, chicken, rat, hamster, octodon, cow, cat, monkey and human) have been immunostained with antibodies against choline acetyltransferase (ChAT), calretinin (CR), calbindin (CB), parvalbumin (PV), GABA and Glycine. Double label immunofluorescence was used to visualize the co-existence of the various immunostains by confocal microscopy. Results:In all species, two ChAT-IR amacrine cells populations were revealed. The one population consisted of the typical "starburst" mirror-symmetric pair of cells occurring in the INL and the GCL with dendritic branching in sublamina a and b respectively of the IPL. In carp, turtle, chicken, squirrel, cat, cow, monkey and human, a second, smaller cell-bodied type of ChAT-IR amacrine was also observed. We call these ChAT2 cells. ChAT2 cells sit high in the INL, above the typical starburst cells and have long dendritic processes ending in stratum 3 of the IPL. ChAT1 starburst amacrine cells colocalize GABA, but in contrast, ChAT2 cells colocalize glycine. Conclusion:Starburst amacrine cells are not the sole amacrine cell type that expresses acetylcholine in the vertebrate retina. Since ChAT2 amacrine cells colocalize glycine instead of GABA, a novel combination of inhibitory and excitatory neurotransmitters will have to be accounted for in retinal circuitry. Supported by DGESIC PB-98-0972 and by Research to Prevent Bllndness.
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