of the snRNA-seq data of the 163 samples identified 17 distinct cell clusters (Fig. 2A, B). Three subtypes of medium spiny neurons (MSNs, the GABAergic projection neurons of the striatum) were identified: D1-type MSNs, D2-type MSNs, and a third subtype marked by both DRD1 and DRD2 expression (D1/D2 neurons). Four small populations of GABAergic interneurons were identified, including parvalbumin-expressing fast-spiking (FS), neuropeptide Y/somatostatin/nitric oxide synthase-expressing low threshold-spiking (LTS), calretinin-expressing (CR), and cholecystokinin-expressing (CCK). A small cluster of cholinergic neurons was also identified (Ach). In addition to neurons, several glial cell populations were observed, including oligodendrocytes (the most prevalent cell type; 28.2% of the nuclei), oligodendrocyte progenitor cells (OPCs), astrocytes, ependymal cells, and microglia. Other cell types included non-microglial macrophages, endothelial cells, and vascular smooth muscle cells.
