Project Summary/Abstract Although males and females both suffer from cocaine use disorder (CUD), females represent a particularly vulnerable population and the neural mechanisms underlying this sex difference remain poorly understood. CUD is characterized by cocaine-induced alterations in dopamine release in the nucleus accumbens (NAc). Sex differences in dopamine release and its regulation in the NAc has also been linked to sex-specific behaviors in CUD. The goal of this proposal is to define sex differences in dopamine release regulation in the NAc and determine how this process is dysregulated following cocaine self-administration. GABA-A and GABA-B receptors in the NAc have been linked to the reinforcing properties of cocaine. Further, GABA is a key regulator of dopamine release through direct actions of GABA receptors on dopamine terminals in the NAc. However, long-term plasticity in GABAergic regulation of terminal dopamine release is unknown, and sex-differences in this process have been virtually unstudied. The goal of this proposal is to define sex differences in GABAergic regulation of dopamine release, determine if cocaine self-administration alters this regulation in a sex-specific fashion, and examine the causal role of GABA-A and GABA-B receptors in cocaine-induced plasticity in the NAc. In Aim 1, I will use ex vivo optical recordings in the NAc with a genetically encoded dopamine sensor (dLight1.2) to record evoked dopamine release in males and females. Using pharmacology, I will investigate GABA-A and B receptor regulation of dopamine release and determine if sex differences exist. Based on my preliminary data, I hypothesize that GABA-A-mediated inhibition of evoked dopamine release will be sex-dependent, with greater effects in males. In Aim 2, I will investigate cocaine-induced plasticity in this regulation following cocaine self- administration in mice. In Aim 3, I will knock out GABA-A and GABA-B receptors in dopaminergic neurons and determine if these receptors are necessary for cocaine-induced plasticity in dopamine release in the NAc. Taken together, the experiments in this proposal will be the first to define sex-differences in GABAergic regulation of dopamine release in the NAc, determine how these processes are altered by cocaine self-administration, and investigate the roles of GABA receptors in cocaine-induced plasticity in NAc dopamine release. This proposal encompasses technical and theoretical training that will provide the foundational expertise and conceptual thinking needed to address larger questions regarding how drug-induced and sex-specific changes in the brain support the development and sustainment of CUD. Additionally, these findings can ultimately inform our understanding of sex-specific mechanisms underlying reward and learning process and lead to more efficacious treatment interventions for males and females.