Fig. 5.

CB1 and D2 distributions in axon terminals forming excitatory-type synapses with D2-labeled dendritic spines. Acb core (A), and Acb shell (B) processed for D2-peroxidase and CB1-gold. Immunogold CB1 labeling (small arrows) is located on the presynaptic plasma membrane of an axon terminal (CB1-t) forming an asymmetric synapse (single curved arrow) with a dendritic spine showing peroxidase reaction product (block arrows) for the D2 receptor (D2-s). The dendrite in A is also contacted (double curved arrow) by an unlabeled terminal (Ut). C: Acb core, processed using the same immunolabels as in A and B. The peroxidase reaction product and immunogold are colocalized in an axon terminal (D2/CB1-t) forming an asymmetric synapse (curved arrow) with a D2-immunoperoxidase labeled spine (D2-s). Within the dually labeled terminal, each marker is distributed away from the presynaptic plasma membrane and in association with small synaptic vesicles (ssv). The spine is apposed by a small unlabeled axon (Ua). Scale bars = 0.5 μm.