The pervasive use of marijuana (cannabis sativa) worldwide, along with its relatively low lethality, has led many to believe that it is of little harm. As such cannabis use currently exceeds that of tobacco smoking among adolescents in the USA. However, is now acknowledged that the developing brain is particularly sensitive to drugs that can impact behavior in adulthood. This is of particular concern given that cannabis is the most commonly abused illicit drug by teens and pregnant women. Our research continues to focus on the impact of ?9-tetrahydrocannabinol (THC), the major psychoactive component of cannabis associated with reward and psychiatric vulnerability. We demonstrated that THC exposure in the developing brain has protracted effects long into adulthood on molecular and behavioral outcomes relevant to reward sensitivity, motivated behavior and negative affect. Our established prenatal animal model mimiced molecular changes in mesocorticolimbic structures to that seen in our human fetal specimens with maternal cannabis use. Moreover, a number of molecular changes relevant to epigenetic disturbances and synaptic plasticity are also commonly evident in adults with adolescent THC exposure emphasizing common underlying mechanisms of developmental THC effects. We identified a specific epigenetic molecular target (Mll1; multiple leukemia ) directly linked to abnormal motivated behavior induced by developmental THC and have developed state-of-the-art strategies such as laser capture microdissection (LCM) to dissect transcriptome and epigenetic alterations in discrete neuronal pathways. We now employ such strategies to delineate pathway-specific alterations of epigenetic mechanisms across the genome associated with developmental THC. Our study focuses on the nucleus accumbens (NAc), which mediates reward, motivated behavior and emotional regulation linked to addiction vulnerability and related psychopathologies. We propose to (1) characterize changes in the epigenome within discrete adult NAc pathways associated with developmental THC exposure and its relationship to transcription using LCM and deep sequencing of chromatin accessibility and overlap with transcriptome data. (2) Establish causal links between molecular alterations identified in specific NAc output pathways wtih behavioral phenotypes relevant to addiction psychopathology. (3) Investigate patterns of adult in vivo neural activity within specific NAc pathways as a consequence of developmental THC exposure using the innovative technique of fiber photometry calcium imaging in a pathway-specific manner. The databases generated from this in-depth body of work will be valuable resources and the results will provide novel insights about the role of specific NAc neural circuits underlying psychopathological vulnerability.