Electron micrographs showing double-labeled PHA-L/VGluT2 axon terminals establishing asymmetric synapses with VTA neurons containing or lacking TH. A1, A2, Two consecutive sections showing that an axon terminal containing PHA-L (peroxidase product) and VGluT2 (immunogold-silver particles) [PHAL(+)/VGluT2(+)] establishes an asymmetric synapse (black curved arrow in A1) with a dendrite (De) containing TH immunolabeling (immunogold-silver particles) [TH(+)]. B1, B2, Two consecutive sections of an axon terminal containing PHA-L (peroxidase product) and VGluT2 (immunogold-silver particles) [PHAL(+)/VGluT2(+)] establishes an asymmetric synapse (black curved arrow in B1) with a dendrite lacking TH immunolabeling [TH(−)]. Scale bar (in B2): 0.2 μm for A1, A2; 0.3 μm for B1, B2.