Extended Data Fig. 6: The Sst^CeA→DA projections.

a, A schematic of the approach. b, Images of the expression of the red fluorescent protein mRuby in Sst⁺ CeA neurons (left) and their projections to the SNc (right) in a representative Sst^Cre mouse as prepared in a. c, A schematic of retrograde tracing with CTB injection into the SNc (left), and an image showing the injection in a representative Sst^Cre;R26^LSL-H2B-GFP mouse (right). d, Confocal images showing the CTB labelled neurons (left), Sst⁺ neurons (middle), and their overlap in the CeA (right). e, Quantification of the Sst⁺ neurons among CTB-labelled neurons in the CeA (n = 8 mice). f, g & h, Same as c, d & e, respectively, except that CTB was injected into the VTA (n = 5 mice). CeL, lateral subdivision of the CeA; CeM, medial subdivision of the CeA. i, A schematic of the approach for anterograde transsynaptic tracing of Sst⁺ CeA neurons. j, Confocal images showing CeA neurons infected by AAV-DIO-EGFP-T2A-TK (left) and HSV-ΔTK-tdTomato (middle), which are the two components of the anterograde transsynaptic tracing system. The “starter cells” are the neurons infected by both viruses (i.e., the yellow cells on the right). k, Confocal images showing the postsynaptic cells labelled by HSV-ΔTK-tdTomato (left panels), which are located in the SNc (top panels) and VTA (bottom panels). The DA neuronal marker tyrosine hydroxylase (TH) was recognized by an antibody (middle panels). Almost none of the HSV-labelled (tdTomato⁺) neurons expressed TH (right panels). l, Quantification of the non-TH cells (which are putative GABAergic neurons) among all the tdTomato⁺ neurons in the SNc and VTA (n = 5 mice). Data are presented as mean ± s.e.m.