then output binary images with a single pixel for each local maxima by choosing an output type of “Single points”. We measured the integrated intensity and calculated the number of grains for each ROI using the “Measure” function within the “ROI Manager”. To quantify DRD1 and DRD2 grains in D1- and D2- MSNs, we used the same method except that we drew ROIs for D1- and D2- MSNs. We confirmed the identity of D1- or D2- MSN instead of a D1/D2-hybrid cell by quantifying the DRD2 or DRD1 and RXFP1 grain number less than three in D1- or D2- MSNs. We used a similar method to quantify ARHGAP6 and GREB1L grains in the core and shell except that we first adjusted the threshold of the images to overexpose the ARHGAP6 and GREB1L signals to guide the ROI drawing. To quantify OPRM1 grain numbers in RXFP1 and CPNE4 islands and nearby D1-MSNs, we labeled DRD1 and OPRM1 on one section and DRD1, RXFP1 and CPNE4 on an adjacent section because of overlapping channels in the OPRM1 and RXFP1 probes. The locations of RXFP1 and CPNE4 islands in the OPRM1 and DRD1 double stained sections were determined by adjacent section labeled with
