Dynorphin (DYN) is an endogenous neurosecretory peptide which exerts its 
activity by binding to the family of G protein-coupled receptors, namely the 
kappa opioid receptor (KOR). Opioids are associated with pain, analgesia, and 
drug abuse, which play a central role in mood disorders with monoamine 
neurotransmitter interactions. Growing evidence demonstrates the cellular 
signaling cascades linked to KOR-mediated monoamine transporters regulation in 
cell models and native brain tissues. This chapter will review DYN/KOR role in 
mood and addiction in relevance to dopaminergic and serotonergic 
neurotransmissions. Also, we discuss the recent findings on KOR-mediated 
differential regulation of serotonin and dopamine transporters (SERT and DAT). 
These findings led to a better understanding of the role of DYN/KOR system in 
aminergic neurotransmission via its modulatory effect on both amine release and 
clearance. Detailed knowledge of these processes at the molecular level enables 
designing novel pharmacological reagents to target transporter motifs to treat 
mood and addiction and reduce unwanted side effects such as aversion, dysphoria, 
sedation, and psychomimesis.