MOLECULAR AND ANATOMICAL DIVERSITY OF NUCLEUS ACCUMBENS NEURONS UNDERLYING MALADAPTIVE REWARD PROCESSING

Neuropsychiatric disorders such as substance use disorders and depression are characterized by maladaptive processing of reward and aversion, processes critically mediated by the nucleus accumbens (NAc). Traditionally, NAc medium spiny neurons (MSNs) are classified based on dopamine D1 or D2 receptor expression; however, this binary framework fails to capture the molecular and functional diversity of these neurons, which can differentially contribute to pathological behaviors. Using single-nucleus RNA sequencing (snRNA-seq), we profiled ~130,000 NAc nuclei from mice exposed to rewarding (sucrose, cocaine) or aversive (foot-shock) stimuli. We identified 22 transcriptionally distinct MSN subclusters with unique gene expression profiles related to synaptic plasticity, metabolic regulation, and mitochondrial function. Importantly, specific MSN subclusters exhibited stimulus-selective transcriptional responses, including a subset uniquely responsive to cocaine exposure, indicating that drug-induced maladaptive plasticity is confined to specialized neuronal populations rather than broadly affecting D1- or D2-MSNs. Building on this molecular atlas, we are anatomically characterizing the identified MSN subclusters using RNAscope-based multiplex in situ hybridization to map their spatial distribution across NAc subregions and their projection patterns. In parallel, we are developing viral tools to selectively label and manipulate these subclusters, which will enable longitudinal monitoring of subcluster-specific activity and causal interrogation of their role in pathological behaviors associated with reward dysregulation. By integrating transcriptomic, anatomical, and functional analyses, this work provides a refined framework for understanding how molecularly and anatomically defined NAc neuronal populations contribute to neuropsychiatric disease. This strategy lays the groundwork for cell-type and circuit-specific therapeutic interventions targeting maladaptive reward and aversion processing.