Fig. 5: Analyses of the synaptic connectivity of Cck⁺ Sp5I neurons.

A–C Schematic diagram showing the viral injection strategy for the retrograde tracing of Cck⁺ Sp5I neurons using a combination of AAV and rabies virus (RV). D, E Representative coronal section showing that the viral injection center, as indicated by the co-expression of EGFP (green) and DsRed (red), was localized in the Sp5I. Note that the double-labeled cells indicate starter cells. F Representative micrographs showing DsRed⁺ cells in the TG. G Schematic diagram showing the viral injection strategy for the anterograde tracing of Cck⁺ Sp5I neurons using AAV-DIO-EYFP. H Representative micrographs showing that AAV-DIO-EYFP efficiently infected Sp5I neurons. I–M Representative micrographs showing EGFP⁺ axonal projections of Cck⁺ Sp5I neurons in different brain regions, including the Sp5O, facial nucleus (7 N), Pr5, gigantocellular reticular nucleus, alpha part (GiA), raphe magnus nucleus (RMg), SC, lateral periaqueductal gray (LPAG), DpMe, retroethmoid nucleus (Reth), PIL, VPM, zona incerta, ventral part (ZIV), and posterior thalamic nuclear group (Po). N Fraction of the total enhanced yellow fluorescent protein (EYFP)-labeled cells in different brain regions that projected from the Cck⁺ Sp5I neurons. Scale bars are labeled in the graphs. Number of mice: three. The data in N are presented as mean values ± SEM. Source data are provided as a Source Data file.