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J.J. O'Brien, S.C. Massey; Connexin36 Forms Gap Junctions Between AII Amacrine Cells and Diffuse ON Cone Bipolar Cells in the Primate Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2333.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: There are many examples of neuronal coupling in the retina. Previously, we and other labs have shown that connexin36 is critical in the rod pathway, coupling AII amacrine cells in the rabbit, mouse and guinea pig retinas (Feigenspan A, et al. 2001, Mills SL, et al. 2001, Guldenagel M, et al. 2001, Deans MR, et al. 2002, Lee EJ, et al. 2003). We also showed that AII amacrine cells are heterologously coupled to the calbindin ON–cone bipolar cells of the rabbit retina using connexin36, at least on the AII side of the gap junction (Mills SL, et al. 2001). Since the macaque primate retina is very similar to the human retina (Haverkamp S, et al. 2003), yet more bipolar cell markers are available for use in the macaque retina, we wanted to determine if AII amacrine cells were heterologously coupled to diffuse ON–cone bipolar cells in the primate retina. Methods: Macaque retinas were dissected, blocked in donkey serum, and incubated in primary antibodies against calretinin, CD15, and connexin36. The tissues were analyzed by triple label confocal microscopy. Structures of particular interest, such as contacts between AII dendrites and On–Cone bipolar cells, were extracted, aligned and signal averaged to obtain the spatial distribution of other labels at these points. Results: Connexin36 immunolabeling was present in both the outer plexiform layer and inner plexiform layer of the macaque retina. In sublamina b of the IPL, Cx36 labeling was prominent in the matrix of the AII amacrine cell dendrites. Cx36 punctate immunolabeling occurred at the dendritic crossovers of the extensive network of AII amacrine cell dendrites. Axon terminals of the CD15 labeled DB6 bipolar cells form a regular array within the IPL. We observed close contacts between CD15 terminals and AII dendrites. Image analysis revealed that Cx36 plaques often occurred at the contact points between CD15 bipolar cells and AII amacrine cells. When DB6 axon terminal contacts with AII amacrine cell dendrites were evaluated by image analysis, a Cx36 peak was correlated with the DB6 and the calretinin AII peaks. When one image channel was rotated, as a control, the AII peak was absent. Conclusions: These results indicate that CD15 is coupled to AII amacrine cells via gap junctions which contain connexin36. It is possible that these heterologous gap junctions may be heterotypic, i.e. assembled by two types of connexin. Thus, Cx36 may only be present on the AII side of the gap junction.
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