SYNAPTIC INPUTS ONTO SMALL-BISTRATIFIED (BLUE-ON/YELLOW-OFF) GANGLION CELLS IN MARMOSET RETINA
Kumiko A. Percival, Paul R. Martin, Ulrike Grünert
The inner plexiform layer of the retina contains functional subdivisions, which segregate ON and OFF type light responses. In monkey retina, color-coding cells called small bistratified cells show blue-ON/yellow-OFF receptive field characteristic. We asked how inputs from ON and OFF bipolar cells are arranged to produce this functional property.
Small bistratified cells are characterized by an extensive inner and a sparse outer dendritic tier (Figure 1). We found that both dendritic tiers receive synaptic input from amacrine and bipolar cells (Figure 2). Our findings are consistent with the idea that the yellow-OFF input derives from bipolar input to the outer tier. Although the inner and outer tiers have different sizes they could provide balanced synaptic inputs serving the blue-ON/yellow-OFF receptive field (Figure 3).
Figure 1: Drawings of small bistratified ganglion cells at different distances from the fovea (given in mm). The outer dendritic tier is shown in red, the inner dendritic tier is shown in grey. The arrow points to the axon. The axon for the cell on the left is not drawn.
Figure 2: Drawings of a small bistratified cell together with its synaptic input. Excitatory (bipolar) input is shown in green inhibitory (amacrine) input is shown in magenta.
Figure 3: Drawing of a small bistratified cell together with the cone photoreceptors in its dendritic field.
Reference: Percival, KA, Jusuf PR, Martin PR, Grunert U (2008). Synaptic inputs onto wide-field ganglion cells in marmoset retina. Proceedings of the Australian Neuroscience Society 18:29.