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Christopher Whitaker, Stephen Massey; Dopamine Regulation of Dye-Coupling in Fountain Amacrine Cells of the Rabbit Retina. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2508.
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© ARVO (1962-2015); The Authors (2016-present)
Over 40 types of amacrine cells have been identified, however, only a handful have been well studied. Of these, their contributions provide distinct and vital roles in retinal signaling including direction selectivity, cross-over inhibition, gap junction regulation, contrast adaptation, and a relay for scotopic signaling. It is highly likely that other, less studied, amacrine cells also contribute to distinct retinal processes. In the current study, we investigated dopamine regulation of dye-coupling in fountain amacrine cells (FAC). This amacrine cell type was previously identified as a GABAergic, medium-field, recurrent amacrine cell (Wright & Vaney, 2000).
FACs were identified with DAPI and dye injected with Neurobiotin in wholemount rabbit retina. Retinas were perfused with or without SCH 23390 (100μM), a dopamine receptor D1 selective antagonist, then injected with Neurobiotin. After a set diffusion period, retinas were fixed and labeled with streptavidin conjugated to Alexa-488 for comparison.
Previous studies have shown that FACs were homologously coupled to 40-50 neighboring cells. We previously reported preliminary data demonstrating that FACs are not coupled by Cx36 or Cx45, suggesting evidence for an additional connexin, responsible for coupling within the IPL. Prior studies have shown that the addition of dopamine decreases coupling in AII amacrine cells through phosphorylation of Cx36. Our current data demonstrate that the blockade of D1 receptors with the drug SCH 23390 increases dye coupling compared to control injected FACs.
FACs are coupled through a yet unknown connexin. Our data suggest that dopamine regulation of amacrine cell dye-coupling follows a common theme regardless of cell type or connexin. Further studies are needed to address the extent of regulation and similarities between other common themes of gap junction modulation.
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