ELECTRON-MICROSCOPIC ANALYSIS OF THE ROD PATHWAY OF THE RAT RETINA

Two immunocytochemical markers were used to label the rod pathway of t he rat retina. Rod bipolar cells were stained with antibodies against protein kinase C and AII-amacrine cells with antibodies against parval bumin. The synaptic circuitry of rod bipolars in the inner plexiform l ayer (IPL) was studied. Rod bipolar cells make approximately 15 ribbon synapses (dyads) in the IPL. Both postsynaptic members of the dyads a re amacrine cells; one is usually the process of an AII-amacrine cell and the other one frequently provides a reciprocal synapse. No direct output from rod bipolar cells into ganglion cells was found. AII-amacr ine cells make chemical output synapses with cone bipolar cells and ga nglion cells in sublamina a of the IPL. They make gap junctions with c one bipolar cells and other AII-amacrine cells in sublamina b of the I PL. The rod pathway of the rat retina is practically identical to that of the cat and of the rabbit retina. It is very likely that this circ uitry is a general feature of mammalian retinal organization.