Dual tracing of inputs to CPu- and NAc-projecting dopamine neurons shows specificity of retrograde labeling and minimal cross talk between circuitry. A, PRV-Introvert-mCherry is identical to PRV-Introvert-GFP except that GFP has been replaced with HA-mCherry. B, Dual injection in the NAc and CPu with isogenic strains of PRV-Introvert results in only a few neurons infected with both viruses (yellow). C, PRV-Introvert-GFP and PRV-Introvert-mCherry were injected into the right NAc and CPu, respectively, of DAT-Cre mice. Four days after injection, brains were assayed for anti-HA (red) and anti-GFP (green) staining. Arrowheads denote neurons expressing both red and green label. Scale bars: 500 μm. Abbreviations are defined in the Figure 3 legend.