Subsequently, another group identified an association between different SNPs in CSNK1E (rs1534891-rs6001093-rs135757) and heroin addiction (Levran et al. 2008). Although the SNPs identified in these two studies are in the same gene, they are not in strong linkage disequilibrium (LD) with each other and presumably must represent distinct functional loci. Nevertheless, taken together these data suggest that this gene is important for both the acute responses to drugs of abuse and substance use disorders. Based on the human data suggesting that CSNK1E might also influence risk for addiction to opiate drugs, we subsequently examined mice with different alleles of Csnk1e and identified a difference in acute sensitivity to the locomotor stimulant effects of the mu-opioid agonist fentanyl (Bryant et al. 2011).
