Project Summary/Abstract Drug abuse is a debilitating chronic disease and it leads to many overdose deaths around the world. Specifically, over 1 million American adults suffer from a cocaine use disorder. Continued drug seeking after abstinence is prevalent despite the devastating personal consequences. Thus, there is an urgent need for the identification of new therapeutic targets for cocaine abuse treatment. Growing body of scientific evidence implicates functional imbalanced in the two medium spiny neuron(MSN) subtypes in the nucleus accumbens, D1-MSNs and D2-MSNs, for the pathology of cocaine abuse. While the examination of molecular and cellular adaptations occurring in NAc D1-MSNs with cocaine exposure has been extensively studied, these adaptations in in NAc D2-MSNs remain largely elusive. In our preliminary data, increased expression of transcription factor Nab2 was observed specifically in D2-MSNs after repeated cocaine exposure in mice. Further, a transcription factor Egr3, which Nab2 functions as its corepressor, was significantly reduced in expression in D2-MSNs. In this proposal, we aim to interrogate the functional role of Nab2 in D2-MSNs in the NAc during cocaine self-administration and cocaine seeking behavior. Specific Aim 1 employs cutting-edge CRISPR tools to inhibit the expression of Nab2 in a D2- MSN specific manner during cocaine self-administration. We will characterize how expression of Nab2 in D2- MSNs contributes to cocaine intake as well as its role in cocaine seeking behavior after short and long term forced abstinence. Specific Aim 2 will utilize RNA sequencing to elucidate the cocaine induced transcriptomic adaptations that occur in D2-MSNs with inhibition of Nab2 expression. Together, the findings from this proposal will shed light on the molecular mechanisms of neuroadaptations occurring during cocaine self-administration and forced abstinence, which has the potential to identify novel targets for cocaine use disorder therapy.