OPRK1, PDYN and OPRM1 have been associated with alcohol use disorders (Edenberg et al., 2008, Schwantes-An et al., 2015, Xuei et al., 2006). Opioid receptors Oprk1 (κ), Oprm1 (μ) and the nociception receptor Oprl1 as well as the prodynorphin gene all had decreased expression (Table 2). These results suggest an increase in pain processing and a reduction in the effectiveness of opioid agonists such as morphine to treat pain. Morphine which can also have anxiolytic effects, has no effect on alcohol withdrawn animals (Silva and Nobre, 2014).
