PDYN mRNA correlated with dynorphin B, the peptide product of this gene (main effect of PDYN mRNA, 0.960 [0.550, 1.400], P = 0.0001; Fig. 4b), while no differences in the level of this endogenous kappa-agonist were found between alcoholics and controls (main effect of alcoholism, 0.052 [−0.128, 0.280], P = 0.605). This evidence concerns the gene PDYN and alcohol drinking.