Purchase this article with an account.
Kaushambi Roy, Abduqodir Toychiev, Stewart A Bloomfield; Gap junctional coupling with amacrine cells underlies the coherent activity between distant retinal ganglion cells evoked by global objects. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified. doi: https://doi.org/.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Coherent spike activity of widely separated retinal ganglion cells (RGCs) has been proposed as a mechanism for encoding global objects (Gray et al., 1989; Neuenschwander & Singer, 1996). Since distant RGCs cannot receive common bipolar cell excitatory drive, we posit that electrical coupling between RGCs and wide field (WF) or polyaxonal amacrine cells (PACs) (Volgyi et al., 2009) is responsible for correlating the spike activity of distant RGCs in response to global stimuli.
Experiments were carried out on adult Kcng4-cre mice in which ON α-RGCs, which are coupled indirectly to PACs, express YFP. Loose patch recordings were made from pairs of ON α-RGCs with non-overlapping receptive fields. Light evoked activity was recorded in response to two discreet rectangles placed over each cell, followed by a large, contiguous rectangle formed by enlarging and fusing the smaller rectangles. Correlated firing was assessed by generating cross-correlogram profiles. Gap junctions (GJs) were blocked with meclofenamic acid (MFA) or 18-β-glycyrrhetinic acid (18-GA), or ablated in Cx36-/- mice in which the GJs between ON α-RGCs and PACs were ablated.
Presentation of a large, contiguous rectangle produced significantly greater correlated spiking between distant ON α-RGCs than evoked by two small rectangles placed over each cell. Enlarging the two, small rectangles in discreet steps towards fusion showed that the correlated activity remained almost constant until the rectangles were 10-20 μm apart, indicating a threshold property. A rectangle placed in the middle of, but not over the center receptive fields of the ON α-RGCs did not evoke activity in either. Application of MFA or 18-GA abolished the increased coherent firing evoked by a large rectangle. Similarly, the increased correlated activity between distant ON α-RGCs was not seen in Cx36-/- mice. Uncoupled RGCs also did not show increased correlated firing to the global rectangle.
Our results indicate that distant RGCs show coherent activity to large objects that is much greater than evoked by separate objects covering each cell. Our data indicate that GJs, presumably those between RGCs and WFACs/PACs, form the excitatory circuitry responsible for the correlated spiking. These results indicate a novel function for inner retinal GJs in the detection and encoding of global object stimuli.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only