Characterization of displaced bipolar cells in the tiger salamander retina

In immunocytochemical studies of the tiger salamander retina, 17% of neurons in the outer nuclear layer did not label for recoverin, a photoreceptor marker. Lucifer yellow injection showed a population of cells in the ONL to be displaced bipolar cells, with axon terminals that stratified exclusively in the OFF sublamina of the inner plexiform layer (IPL), and predominately within the cone-dominated region of the OFF sublamina. Glutamate generated a dendritic cationic conductance increase in all displaced bipolar cells tested, and typical cone-dominated bipolar cell light responses were observed among displaced cells that stratified in the central IPL. We conclude that displaced bipolar cells in the tiger salamander retina are entirely OFF-center cells, and predominately cone-dominated cells.