Figure 10.

Ultrastructural analysis of multisynaptic hippocampal axon in the nucleus reuniens. Photomicrographs from serial EM depict ultrathin (50 nm) sections through RE (case BU, CBL tracer). Together they depict a hippocampal axon forming a multisynaptic complex with multiple dendrites in RE. A–G, The hippocampal termination (blue) forms an asymmetric synapse (white arrow) with an inhibitory dendrite (pink), which contains pleomorphic vesicles (double-headed arrows in A), presumed to emerge from a local inhibitory neuron. H–J, The hippocampal termination forms asymmetric synapses (white arrows) with two new inhibitory dendrites (purple, yellow). K–R, The hippocampal termination forms a perforated asymmetric synapse (white arrows) with the shaft of an excitatory dendrite (green) positive for CB (labeled with gold, which forms black clusters, asterisks). S–Y, The hippocampal termination forms an asymmetric synapse (white arrows) with a thorn (green) from the CB-positive excitatory dendrite. CBL, Cascade Blue; Hipp, hippocampus.