SYNAPTIC CONNECTIONS OF ROD BIPOLAR CELLS IN THE INNER PLEXIFORM LAYER OF THE RABBIT RETINA

We have reconstructed from electron micrographs of a continuous series of thin sections the synaptic connections of the axonal arborizations of all the rod bipolar cells contained in a small region of the retina of the rabbit. We observed that all rod bipolars share the same pattern of connectivity and are probably functionally equivalent. As a rule, they do not contact ganglion cells. Their prevalent synaptic output is on narrow‐field, bistratified, and indoleamine‐accumulating amacrine cells. Their dominant inputs are the reciprocal synapses from the indoleamine‐accumulating amacrines, but they also receive a sizable number of synaptic contacts from other, non‐reciprocal, amacrine cells. The lateral spread of scotopic signals at the synapse between rod bipolars and narrow‐field, bistratified amacrines is small. Finally, in the rabbit, as in the cat, a narrow‐field, bistratified amacrine is inserted in series along the rod pathway. Copyright © 1990 Wiley‐Liss, Inc.