Supplementary Figure 6: Mouse mesoaccumbens neurons establish VGluT2-asymmetric synapses or TH-symmetric synapses (TH::Cre mice).

(a) Schematic representation of AAV5-DIO-ChR2-mCherry injection into the VTA of TH::Cre mice. (b) Electron micrograph of a nAcc AT from a VTA neuron co-expressing mCherry-IR (scattered dark material) and VGluT2-IR (gold particles, green arrowheads) making an asymmetric synapse (green arrow) with a dendrite (De). (c) Electron micrograph of an AT from a VTA neuron co-expressing mCherry-IR (scattered dark material) and TH-IR (gold particles, blue arrowhead) making a symmetric synapse (blue arrow) on a dendrite (De). (d) Schematic representation of nAcc inputs from VTA neurons expressing mCherry-IR under the regulation of TH promoter (TH-ChR2-mCherry mice). (e-g) A single AT from a VTA-VGluT2 neuron synapses on several postsynaptic structures. Serial sections of a single AT derived from a VTA neuron expressing mCherry-IR (scattered dark material) and containing VGluT2-IR (gold particles, green arrowheads) establishes asymmetric synapses (green arrows) with several postsynaptic structures, two dendritic spines (sp1 and sp2) and one dendrite (De). Scale bars represent 200 nm (b,c,e,f,g).