Relative Timing Between Kappa Opioid Receptor Activation and Cocaine Determines the Impact on Reward and Dopamine Release.
Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology March 1, 2016 Elena H Chartoff, Shayla R Ebner, Angela Sparrow et al.
Activating kappa opioid receptors (KOR) in rats produces a biphasic effect on cocaine's rewarding properties. When cocaine was given within an hour of the KOR agonist salvinorin A, the drug's rewarding effects and dopamine release were amplified. However, when cocaine was administered 24 hours later, these effects were diminished. The study also found changes in gene expression and dopamine levels in brain reward regions at the 24-hour mark. The authors propose that KOR activation, which occurs during cocaine withdrawal, may time-dependently alter vulnerability to cocaine's effects.