Tracer coupling pattern of amacrine and ganglion cells in the rabbit retina

Abstract

We examined the tracer coupling pattern of more than 15 morphological types of amacrine and ganglion cells in the rabbit retina. Individual cells were injected intracellularly with the biotinylated tracer Neurobiotin, which was then allowed to diffuse across gap junctions to label neighboring neurons. We found that homologous and/or heterologous tracer coupling was common for most proximal neurons. In fact, the starburst amacrine cell was the only amacrine cell type that showed no evidence of coupling. The remaining types of amacrine cell were coupled exclusively to other amacrines, either homologously or, more often, through a combination of homologous and heterologous junctions. In only one case did we visualize labeled ganglion cells following injection of Neurobiotin into an amacrine cell. In contrast, injection of Neurobiotin into ganglion cells almost always resulted in the labeling of amacrine cells. Taken together, these results suggest a directionality to the movement of tracer across gap junctions connecting amacrine and ganglion cells. We found that the coupling pattern for a given morphological type of cell was generally stereotypic and consistent across retinas. The notable exceptions to this finding were alpha ganglion cells and cells with morphology corresponding to that of on-off direction selective ganglion cells. In both cases, individual cells showed either extensive coupling to both amacrine and ganglion cells or no coupling at all. A notable finding was that, in every case, the neighboring cells within a tracer-coupled array were always within one gap junction of the injected neuron. Furthermore, in many cases, the array formed by the somata of tracer-coupled cells was almost perfectly coincident with the dendritic arbor of the injected cell. Thus, our results indicate that whereas coupling is extensive within the proximal retina, individual cells partake in coupled networks that are stereotypic and highly circumscribed.

Molecular Phenotyping of Retinal Ganglion Cells

“…1 A) and ranging from Ͻ50 M to ϳ10 mM, characterizes different compartments. The basic reasons for this differentiation are that some ganglion cells contain no GABA; displaced starburst amacrine cells contain GAD65 (Brandon and Criswell, 1995) and synthesize high GABA levels; Müller cells import GABA via a high-affinity GAT-3 transporter (Johnson et al, 1996) and metabolize it, yet have a persistent low level; and many ganglion cells engage in heterologous dye coupling with amacrine cells (Xin and Bloomfield, 1997), and GABA could clearly leak into ganglion cells. The concentration scaling of this image reveals that Müller cells appear to contain ϳ85 M GABA (uncorrected for fixation loss) and that some large neuronal cells clearly contain measurably less than that, whereas others contain much more.…”

A model of high-frequency oscillatory potentials in retinal ganglion cells

“…In addition, both alpha cells and M cells exhibit a high-frequency resonance in their temporal modulation transfer functions (Frishman et al, 1987;Solomon et al, 2002). HFOPs are also present in the rabbit retina (Ariel et al, 1983), where tracer coupling between ganglion cells and amacrine cells has also been described (Xin & Bloomfield, 1997).…”

Dopaminergic modulation of tracer coupling in a ganglion-amacrine cell network

“…Xin and Bloomfield (1997) showed drawings of two different morphological types of amacrine cell and found a bimodal distribution of soma diameters. The more intensely-stained amacrine cell, which we call AC1, was, on the average, the larger of the two.…”

“…Evidence for direct coupling between neighboring AC1 cells comes from Xin and Bloomfield (1997), who injected cells resembling AC1 cells morphologically and found coupling to neighboring cells of the same type, with or without additional coupling to ganglion cells. However, it was uncertain whether the cells they injected were the same type as those coupled of OFF α ganglion cells.…”