This study shows that the DEGs that are implicated in the development of opioid dependence and addiction in the winners are Oprk1 in the VTA (upregulation) and STR (downregulation); Oprd1 (upregulation) in MRNs and Oprd1 and Penk (upregulation) in the PFC; Pdyn gene (upregulation) in the NAcc as well as Th, Ddc, Slc6a2, Slc6a3, and Snca in the VTA (upregulation) and Drd2 and Pdyn (upregulation) in the NAcc. The gene discussed is PENK; the disease is opiate dependence.