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J. Zhang, S.M. Wu; Connexin 36 Mediates Photoreceptor Coupling in the Tiger Salamander Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4158.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: It has been shown that rods in the salamander retina are strongly coupled with adjacent rods and weakly coupled with adjacent cones (Attwell et al, J. Physiol 352:703-737, 1984). The objective of this study is to understand the anatomical and molecular basis of gap junctions between rods and between rods and cones in the retina. Methods: Expression and cellular localization of connexin 36 (Cx36) were studied by Western-blot and immunocytochemistry in conjunction with confocal microscopy. The location and ultrastructure of gap junctions between neighboring retinal cells was examined by electron microscopy (EM). Results: Western blot analysis showed that Cx36 protein was expressed in the tiger salamander retina, and immuocytochemical data demonstrated that Cx36 was present in the outer nuclear layer and both synaptic layers. In the wholemount retina, Cx36-positive plaques were observed between neighboring rods, and they outlined the cell boundaries of the rod mosaic at a level distal to the external limiting membrane. Among 139 rods, 7% coupled with 3, 72% coupled with 4, and 21% coupled with 5 adjacent rods. On average, each rod contained 19±3 Cx36-positive plaques. Cx36-positive plaques were also observed between some cones and their adjacent rods, but they were fewer and smaller compared with those between rods. EM analysis revealed that gap junctions were located between the radial fins of adjacent rods and between cone and rod fins. Double label experiments showed that some Cx36-positive plaques in the outer plexiform layer were located on rod telodendrites or underneath cone pedicles, but not on horizontal cell processes. Conclusions: Our results suggest that connexin 36 mediates photoreceptor coupling by forming gap junctions between rods and between rods and cones in the tiger salamander retina. The function of connexin 36 in the outer and inner plexiform layers is not clear.
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