Localization of AMPA-selective glutamate receptor subunits in the cat retina: a light- and electron-microscopic study

The distribution of AMPA-selective glutamate receptor subunits was studied in the cat retina using antisera against GluR1 and GluR2/3. Both antisera were localized in postsynaptic sites in the outer plexiform layer (OPL) as well as the inner plexiform layer (IPL). Immunoreactivity for GluR1 was seen in a subpopulation of OFF cone bipolar cells and a number of amacrine and ganglion cells. Within the IPL, processes staining for GluR1 received input from OFF and ON cone bipolar cells but not from rod bipolars. Labeling for GluR2/3 was seen in horizontal cells, an occasional cone bipolar cell, and numerous amacrine and ganglion cells. In the IPL, GluR2/3 staining was postsynaptic to cone bipolar cells in both sublaminae. AII amacrine cells which receive rod bipolar input were also labeled for GluR2/3. With both antisera, staining was limited to a single member of the bipolar dyad complex, providing morphological evidence for functional diversity in glutamatergic pathways.