Fig. 7.

Electron micrographs showing TH-labeled terminals within the PFC directly apposed to PRV-labeled dendritic spines without forming distinct synaptic specializations. In A, a PRV-labeled spine (PRV-s) emanates from a dendrite that also contains immunogold labeling for PRV (PRV-d). The labeled spine receives an asymmetric synapse (curved arrow) from an unlabeled terminal (Ut) and is also contacted (straight arrow) by a TH-labeled terminal (TH-t). Serial sections (B, C; D, E) illustrate two PRV-labeled spines that receive asymmetric synaptic contact from unlabeled terminals as well as appositional contact from TH-labeled terminals. In D andE, the TH-labeled terminal is directly apposed to the unlabeled terminal. Scale bar, 0.25 μm.