Synaptic patterns and response properties of bipolar and ganglion cells in the cat retina.

After intracellular recording, bipolar cells of the cat retina have been stained with HRP and their contacts in the outer and inner plexiform layers examined by electron microscopy. Rod bipolars and cone bipolar cb6 make invaginating, ribbon related contacts with photoreceptors, hyperpolarize in response to light, and have axons terminating in layer b of the IPL. The axon terminal of cb2 ends in layer a of the IPL and its basal contacts with cones mediate hyperpolarizing light-responses. Cone bipolar cb5 is a center-depolarizing type with an axon ending in layer b but its cone contacts are at semi-invaginating basal junctions. Except for the amacrine-contacting rod bipolar cell, all cone bipolar types synapse with both amacrine and ganglion cells in the inner plexiform layer. In addition cb5 contacts AII amacrine cells with large gap junctions, and is physiologically rod dominated.