The nucleus accumbens plays a central role in ther regulation of reward, emotion, motivation and goal-directed behavior. Gene expression impairments in this brain region are of crucial interest to understand the neurobiological underpinnings of heroin use disorder. We used the Affymetrix HG-U133A microarray to assess gene expression in the post-mortem nucleus accumbens of human heroin users and control subjects and identified differentially expressed genes. Overall design: Human brains from apparent heroin overdose and normal control Caucasian subjects without head trauma were collected at autopsy with 24 hours of death. Cause of death was determined by forensic pathologist