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EB Trexler, W Li, SC Massey; Gap Junction Coupling between Cone Bipolars and AII Amacrine Cells . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1943.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Gap junctions couple homologous cell types, forming lateral networks of neurons that synapse with vertical processing units in both the outer and inner plexiform layers of the retina. In addition, gap junctions couple heterologous cell types such as AII amacrine cells (AIIs) and on-center cone bipolars (CBs). Functional coupling of AIIs to each other and CBs to AIIs is known to be important for scotopic vision. Recent studies in light adapted retinas suggest that AII-CB junctions may also operate under photopic conditions. However, little is known about the electrical conductance and gating properties of AII-CB gap junctions. Methods: Using two patch electrodes, we recorded from pairs of AIIs and CBs in light-adapted rabbit retina. Stable whole cell patch recordings were obtained on each cell in the pair, and each cell was held at -40 or -60 mV. Voltage pulses were applied to one cell in the pair, and junctional currents were measured in the opposite cell. Results: Gap junction coupling varied in conductance from ∼50 to more than 600 pS. In some pairs, it appeared that the instantaneous junctional conductance rectified, with conductance greatest when the AII was depolarized relative to the CB. Single channel gating events were not evident, suggesting a small single channel conductance. Conductance decreased over a period of minutes, suggesting that dialysis with the pipette solution removes factors necessary for normal operation. Conclusion: These experiments demonstrate that a direct electrical connection exists between AII amacrine cells and ON cone bipolars. Furthermore, the gap junctions between AIIs and CBs are open under light-adapted conditions and allow bi-directional electrical signaling between the two cell types.
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