Many diverse types of retinal neurons show tracer coupling when injected with biocytin or Neurobiotin

This study demonstrates that the junctional connections between rod-signal interneurons in mammalian retina can be visualized by tracer coupling, following intracellular injection of the biotinylated compounds, biocytin and Neurobiotin. In addition, many other types of retinal neurons - including B-type horizontal cells and several types of retinal ganglion cells - show specific patterns of tracer coupling, usually to cells of the same neuronal type but occasionally to cells of other neuronal classes. These findings suggest that electrotonic transmission occurs commonly throughout the retina and, consequently, diverse types of retinal neurons may form functional networks of coupled cells.