The kappa opioid receptors have widespread distribution in the central nervous system and play a role in a wide variety of physiological systems, including pain regulation, addiction to drugs of abuse, neuroendocrine regulation, cardiovascular function, respiration, temperature regulation, feeding behavior, and stress responsivity (e.g. Bruchas et al. 2010; Knoll and Carlezon 2010; Kreek et al. 2005). Kappa opioid receptors play an important role in modulation of opioid, cocaine and other rewarding stimuli, presumably through modulation of basal and drug-induced dopaminergic tone (Kreek et al. 2002). Oprk1 knockout mice showed elevated basal dopamine release in the nucleus accumbens and enhanced cocaine-induced dopamine levels compared to wild-type mice, suggesting association with greater vulnerability to cocaine abuse (Chefer et al. 2005) (also see PDYN section below).
