OPRK1 and alcohol drinking: Given the role of NAc in different affective and addiction disorders, the presence of KOR/DYN system in the NAc and the changed regulation of KOR/DYN in the brain during AUD, it is feasible that KOR/DYN changes in the brain are altered by epigenetic modification and neuroadaptation caused by long term alcohol use (Wee and Koob, 2010).