Shared and divergent transcriptomic regulation in nucleus accumbens D1 and D2 medium spiny neurons by cocaine
Substance use disorders (SUDs) induce widespread molecular dysregulation in nucleus accumbens (NAc), a brain region pivotal for coordinating motivation and reward, which is linked to neural and behavioral disturbances promoting addiction. Despite the overlapping symptomatology of SUDs, different drug classes exert partly unique influences on neural circuits, cell types, physiology, and gene expression. To better understand common and divergent molecular mechanisms governing SUD pathology, we characterized the cell-type-specific restructuring of the NAc transcriptional landscape after psychostimulant or opioid exposure. We combined fluorescence-activated nuclei sorting and RNA sequencing to profile NAc D1 and D2 medium spiny neurons (MSNs) across cocaine exposure paradigms, including initial exposure, prolonged withdrawal after repeated exposure, and re-exposure post-withdrawal. Our analyses reveal that D1 MSNs display many convergent transcriptional responses across the two drugs, whereas D2 MSNs manifest highly divergent responses, with morphine causing far more adaptations in this cell type. Overall design: Male double-transgenic mice expressing D1- or D2-specific nuclear-tagged GFP were generated by crossing LSL-eGFP::L10a (IMSR_JAX:022367) mice with either D1-Cre (MGI:3836633) or D2-Cre (MGI:3836635) mice. Cocaine hydrochloride (from the National Institute on Drug Abuse) were dissolved in 0.9% saline and administered intraperitoneally at doses of 20 mg/kg. In the cocaine cohort, mice received saline or cocaine each day for 10 days prior to withdrawal. As depicted in Figure 1A, after 30 days of homecage withdrawal, mice received challenge injections of saline, cocaine and were sacrificed 1 h later. Brains were extracted, the NAc was dissected, and samples underwent fluorescence-activated nuclei sorting to purify nuclei for D1 or D2 MSNs. RNA was then extracted from nuclei, and RNAseq was performed.