Mammalian Retinal Ganglion Cell Dendritic Contact Loop And Receptor Development

This study was aimed to examine the relationship between dendrites of direction-selective (DS) ganglion cell and processes of starburst amacrine cell in rabbit retina and to see how the dendritic interaction could contribute to the DS mechanism. Responses of DS cell to moving light bar in different directions were recorded using whole cell patch clamp technique on the rabbit retina. After recording, DS cells were filled with neurobiotin. SA cells were intracellular injected with a sharp electrode containing Lucifer Yellow. Cholinergic plexus were labeled with an anti-VAChT antibody. ON and ON-OFF DSGCs were found to exhibit tight dendritic cofasciculation with the cholinergic plexus. The degree of cofasciculation of both types of DSGC dendrites and cholinergic plexus was found to be significant, unlike the relationship between non-DS cells and the cholinergic plexus, which was close to chance distribution. No difference was observed in the degree of cofasciculation in different regions of the DS dendritic field. Individual SAs intracellularly injected both on the 'preferred'and 'null'side of the DSGCs showed the same degree of cofasciculation with the DSGCs. We conclude that the computation of motion direction is unlikely to result from apparent asymmetry in geometric proximity between SAs and DSGCs. Highly selective synaptic connections between SAs and DSGCs are necessary.