Marks a Spatially and Transcriptionally Unique Population of -Expressing Neurons in the Nucleus Accumbens.

Opioids produce addictive, analgesic, and euphoric effects via actions at mu opioid receptors (μORs). The μOR is encoded by the gene and is expressed in multiple brain regions that regulate reward and motivation, such as the nucleus accumbens (NAc). expression in NAc medium spiny neurons (MSNs) mediates opioid place preference, seeking, and consumption. However, recent single nucleus RNA sequencing (snRNA-seq) studies in rodent, primate, and human NAc have revealed that multiple subpopulations of NAc neurons express mRNA, making it unclear which populations mediate diverse behaviors resulting from μOR activation. Using published snRNA-seq datasets from the rat NAc, we identified a novel population of MSNs that express the highest levels of of any NAc cell type. Here, we show that this population is selectively marked by expression of , a gene encoding a carbohydrate sulfotransferase. To validate this observation and characterize spatial localization of this population in the rat NAc, we performed multiplexed RNAscope fluorescence hybridization studies to detect expression of and mRNA along with well-validated markers of MSNs. Notably, + neurons exhibited more abundant expression of as compared to other cell types, and formed discrete cellular clusters along the medial and ventral borders of the NAc shell subregion. Moreover, mRNA was also found to mark specific MSN populations in published human and primate snRNA-seq studies, indicating that this unique population may be conserved across species. Together, these results identify a spatially and transcriptionally distinct NAc neuron population characterized by the expression of . The abundant expression of in this population and the conservation of these cells across species suggests that they may play a key functional role in opioid response and identify this subpopulation as a target for further investigation.