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Dennis M Dacey, Yeon Jin Kim, Orin S. Packer, Peter B Detwiler; ON-OFF direction selective ganglion cells in macaque monkey retina are tracer-coupled to an ON-OFF direction selective amacrine cell type. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5280.
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In the macaque monkey retina a single ganglion cell type, the recursive bistratified cell, shows ON-OFF direction selectivity (Detwiler et al., ARVO abstr, 2019). Intracellular injection of Neurobiotin showed previously that recursive bistratified cells are tracer-coupled to amacrine cells with large somas (Dacey, et al., ARVO abstr. 899, 2010). These cells were tentatively identified as the axon-bearing, spiking ON-OFF A1 amacrine cell type (Dacey, J.Comp.Neurol. 284;275, 1989) (Fig. top). In correspondence the A1 amacrine cell shows apparent tracer-coupling to a single low-density ganglion cell type. Our purpose was to record from A1 amacrine cells and determine if they are in fact coupled to the recursive bistratified ganglion cell and thus contribute to a direction selective circuit in the primate.
A1 amacrine cells were targeted for intracellular recording in the in vitro macaque retina by their large soma size. Recording pipettes contained the tracer Po-pro-1 in order to observe tracer-coupling in vitro (Hoshi et al., J. Hist. Cyt, 54;1169, 2006). Directional tuning in A1 cells was determined with drifting gratings or moving bars; a direction selective index (DSI) was given by the difference in the responses to preferred vs null direction stimuli.
When A1 amacrine cells are filled with Po-pro-1 a tracer-coupling pattern is revealed in vitro identical to that observed previously after Neurobition injections and post-fixation HRP histochemistry (Stafford and Dacey, Vis. Neurosci. 14;507,1997). A1 cells are Po-pro tracer-coupled to neighboring A1 cells as well as a single low-density ganglion cell type with a small cell body. Po-pro-1 coupled ganglion cells were targeted for intracellular recording and shown to be ON-OFF direction selective recursive bistratified ganglion cells. A1 amacrine cells exhibit transient depolarizations and spikes at light ON and OFF and are strongly direction selective for both membrane potential amplitude and spike discharge (n = 9; Fig. bottom).
A1 amacrine cells are tracer-coupled to the ON-OFF direction selective recursive bistratified ganglion cell. Like the coupled ganglion cells the A1 cells are transient, ON-OFF direction selective. The spiking A1 amacrine appears to participate in newly identified direction selective circuitry in the primate retina.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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