One of the most remarkable features of the DRD1 and DRD2 labelling in the VS was the presence of D1-exclusive islands that likely corresponded to “interface islands” (Figure 6A).34,35 We investigated whether the cell types within these D1-exclusive islands corresponded to the smaller DRD1 enriched VS clusters (Figure 2A, light and dark orange). We selected two respective marker genes, RXFP1 and CPNE4, for the two DRD1 enriched VS clusters (Figure S6C). We labeled one section using DRD1, RXFP1, and CPNE4 probes and revealed that RXFP1 and CPNE4 labeled distinct D1-exclusive cell islands (Figure 6B). High resolution confocal microscopy of these islands verified that CPNE4 and DRD1 co-localized in the same cells in one island (Figure 6C), whereas RXFP1 and DRD1 co-localized in the same cells of another island (Figure 6D). These results suggest that different interface islands contain different DRD1-positive cell types.
