Single-cell sequencing of rodent ventral pallidum reveals diverse neuronal subtypes with noncanonical interregional continuity

The ventral pallidum (VP) was defined as a basal ganglia nucleus with dense input from ventral striatum. To further investigate its regional identity, we conducted a cross-species transcriptional characterization of VP cell types. We performed single-nucleus RNA sequencing of VP tissue from mice and rats and identified 16 conserved VP neuronal subclasses, including 14 γ-aminobutyric acid-releasing subclasses from three developmental classes. Combining our sequencing data with a spatial atlas revealed that all VP subclasses extended beyond the traditional borders in VP. Integrating our VP data with published striatal, hypothalamic, and extended amygdalar sequencing confirmed that cell types are shared among these regions. Given the role of VP in feeding, we also assessed the transcriptional impact of high-fat diet, which altered expression of genes involved in oxidative phosphorylation and inhibitory signaling. Overall, our results demonstrate that VP is not a transcriptionally discrete nucleus; rather, VP contains cell types with diverse expression patterns overlapping with regions beyond the basal ganglia.