Rod and cone inputs to bipolar cells in goldfish retina

Five morphological types of bipolar cells which make synaptic contact with rods and cones are distinguished in the retina of adult goldfish (Carassius auratus) by characteristics readily observable in the light microscope. Cells were designated type a or type b according to whether their axons terminate in the distal part (sublamina a) or proximal part (sublamina b) of the inner plexiform layer, respectively. Analysis of serial semi-thin sections of Golgi-impregnated cells demonstrates that each subtype of bipolar cell contacts rods and a characteristic set of chromatic subtypes of cones: types a1 and b1 cells contact rods and red-sensitive cones, while types a2, b2, and b3 contact rods and red- and green-sensitive cones. Comparison with published descriptions of cells stained with Procion Yellow after intracellular recordings had been made suggests that type a cells should be off-center types and type b on-center. Furthermore, it is suggested that the receptive fields of cell types a1 and b1 should be non-color-coded, and those of a2, b2, and b3 color-coded.