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Ji-Jie Pang, David Paul, Samuel Wu; Gap-junctions between Populations of Ganglion and Amacrine Cells in the Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3390.
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© ARVO (1962-2015); The Authors (2016-present)
Retinal amacrine cells (ACs) may make inhibitory chemical synapses and potentially excitatory gap junctions with ganglion cells (GCs). To understand the overall strength of the coupling between retinal GCs and ACs and to test whether all ACs within individual immunological subpopulations are identically coupled with GCs, we investigated the total number and subtypes of ACs coupled to the entire GC population.
Wild type and three lines of transgenic mice were studied. GCs and GC-coupled ACs were identified by the previously established LY-NB (Lucifer yellow- neurobiotin) retrograde double-labeling technique and specific antibodies. The labeled whole retinas and vertical slices were examined with a confocal microscope.
GC-coupled ACs (NB-positive and LY-negative) comprised nearly 11% of displaced ACs and 4% of conventional ACs in wild-type mice. They were 9% and 4% of displaced ACs in Cx45-/- and Cx36/45 -/- mice, respectively. Somas of these ACs were small in Cx36/45 -/- mice but variable in other strains. GC-coupled ACs were mostly GABA-immunoreactive (IR) and located in the GC layer. A minority of ACs in various AC subpopulations was revealed to couple with GCs, including GABA-IR, glycine-IR, calretinin-IR, 5-HT-accumulating and ON-type ChAT ACs in wild-type and choline acetyltransferase (ChAT) transgenic mice (ChAT- tdTomato). In the distal 80% of the IPL, dense GC dendrites coexisted with rich glycine-IR and GABA-IR. In the inner 20% of the IPL, sparse GC dendrites coexisted with a major GABA band, sparse glycine-IR and PKCα-IR globules.
Our data revealed for the first time that various AC subtypes could couple to GCs, but ACs of the same immunoreactivity may either couple or not couple to GCs. Cx36 and Cx45 dominate GC-AC coupling except for small ACs. The overall potency of GC-AC coupling was moderate, especially in the proximal 20% of the IPL, where inhibitory chemical signals are dominated by GABA ACs.
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