Prodynorphin is the precursor for the opioid peptides alpha- and beta-neoendorphins, dynorphin A and dynorphin B, which are endogenous ligands for the kappa opioid receptor. Dynorphin peptides decrease basal and drug-induced dopamine levels in several areas of the dopaminergic, nigrostriatal, and mesolimbic–mesocortical systems. Expression of the PDYN gene is increased by cocaine (for a recent review see Yuferov et al. 2010). Pdyn knockout mice showed increased explorative behavior in anxiety tests demonstrating the anxiogenic role of prodynorphin-derived peptides (Wittmann et al. 2009).
