PNOC and opiate dependence: Xuei et al. (160) assessed correlations between SUDs and polymorphisms in OPRL1 as well as in the prepronociceptin gene (PNOC), which encodes the NOP receptor precursor, in a European American population; rs6512305 and rs6090043 were nominally associated with opioid dependence; however, no SNPs proved significant (160).