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Z. Yang, J. Zhang, S.M. Wu; Synaptic Contacts Between Photoreceptors and ON Bipolar Cells in the Tiger Salamander Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4179.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To study rod/cone synaptic inputs, photoreceptor-bipolar cell convergence and patterns of axon terminal ramification of ON bipolar cells in the tiger salamander retina. Methods: Immunocytochemical experiments were performed on salamander retinas with confocal microscopy. ON bipolar cells were labeled with antibodies against Goα (Chemicon, Inc). Photoreceptors were identified using antibodies against recoverin (kindly provided by Dr. A. M. Dizhoor). Topro 3, a nuclear dye ( Molecular Probes), was used for bipolar cell body labeling. Results: Recoverin antibody differentially labels rod and cones: it weakly stained rod cell bodies, axons and synaptic spherules and heavily stained cone cell bodies and pedicles. The majority of the ON bipolar cells are Goα-positive, with axon terminals ramified mainly in strata 6-9 and a minor band in stratum 3 of the inner plexiform layer (IPL). Stratum 10 of the IPL is Goα-negative and previous studies showed that axon terminals of rod-dominated ON bipolar cells ramified in that stratum. The axonal morphology of Goα-positive cells resembles that of the cone-dominated or mixed rod/cone ON bipolar cells (DBCCs and DBCMs). The Goα-positive dendritic processes make close contacts with all cone pedicles and superficial contact with some rod spherules, consistent with the idea that Goα subunits are present in DBCCs and DBCMs. On average, the diameter and density of Goα-positive cell bodies were 8.64±1.62µm and 3198±895 cells/mm2 (n=84), respectively, which account for about 41% of the nuclei in the distal inner nuclear layer. The spatial distribution of rods, cones and Goα-positive cells were also studied. Conclusions: Our results suggest that Goα labels the majority of ON bipolar cells in the salamander retina. The Goα-positive cells contact all cones and a subpopulation of them receive rod inputs as well. Rod-dominated ON bipolar cells are Goα-negative and they may contain different G protein subunits.
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