Synaptic pattern of AMPA receptor subtypes upon direction-selective retinal ganglion cells

In the search for anisotropies that might contribute to a directional preference of direction-selective (DS) retinal ganglion cells (RGCs), we studied the distributions of AMPA receptor subtypes GluR1, GluR2/3, and GluR4 upon the dendritic arbors of DS RGCs of the rabbit with antibody immunocytochemistry. DS RGCs were injected with Lucifer yellow and the cells were identified by their characteristic morphology. The double-labeled images of dendrites and receptors were visualized by confocal microscopy and were reconstructed from high-resolution confocal images. We found no evidence of asymmetry in any of the AMPA receptor subunits examined upon the dendritic arbors of both On and Off layers of DS RGCs. The present results indicate that direction selectivity appears to lie in presynaptic pattern.