Figure 7: Neurotransmitter phenotypes and synaptic structure of VTA afferents.

(A) Upper left, schematic of injection of CTB into VTA to label Aiv_VTA neurons. Upper right, Aiv_VTA projecting neurons (magenta), VGLUT2 (green), and VGAT (red), scale bar 50 μm. Bottom left, higher magnification views, all scale bars 10 μm. Bottom right, pie chart of percentage of Aiv_VTA cells positive for VGLUT2, VGAT, both, and neither (gray). (B) Upper left, schematic of injection of CTB into VTA to label VP_VTA neurons. Upper right, VP_VTA projecting neurons (teal), VGLUT2 (green), and VGAT (red), scale bar 50 μm. Bottom left, higher magnification views, all scale bars 10 μm. Bottom right, pie chart of percentage of VP_VTA cells positive for VGLUT2, VGAT, both, and neither. (C) Left, viral injection of GFP into Aiv to express in Aiv_VTA terminals. Top middle and right, PV+ (red) and TH+ neurons (pink) respectively with Aiv terminals (green) in VTA, scale bar 50 μm. Bottom middle and right, higher magnification view showing Aiv terminals in apposition to PV+ (middle, red) and TH+ (right, pink) cell bodies, scale bar 10 μm. (D) Same as (C) but for VP_VTA GFP terminals. (E) Top, bar graph of appositions from Aiv_VTA GFP terminals on PV+ (red) and TH+ (pink) cells in the VTA. Bottom, same as (E) but for VP_VTA GFP terminals onto VTA neurons. (F) Upper Left, schematic of injection of CTB into VTA and VP to retrogradely label Aiv_VTA neurons and Aiv_VP neurons. Bottom left, pie chart of overlap of Aiv_VP neurons with Aiv_VTA neurons. Top right, Aiv_VTA (red), Aiv_VP (green), and co-localized (yellow) neurons, scale bar 200 μm, sagittal view with the song nucleus RA outlined. Bottom right, higher magnification view, scale bar 50 μm.