Fig. 3.

Ultrastructure of dendro-dendritic contacts between CR-IR dendrites. In A, C, and D, zonula adherentia (arrowheads) are formed between the contacting dendrites. In C and D, one of the CR-IR dendrites receives an additional axo-dendritic contact (white arrow, symmetrical synapse), next to the punctum adherens, from CR-IR axon terminals. The dendrites also receive asymmetrical synapses from unlabeled terminals (curved white and black arrowin A). The membrane segments labeled with double arrowheads in B appear to form a gap junction. However, because of the diamino-benzidine precipitate on the membranes, the type of the specialization is equivocal. Scale bars: A,B, 0.5 μm; C, D, 0.25 μm.