Evaluation of the agonist PET radioligand [11C]GR103545 to image kappa opioid receptor in humans: Kinetic model selection, test-retest reproducibility and receptor occupancy by the antagonist PF-04455242

[11C]GR103545 PET can be used to image and quantify KOR in humans, although it has slow kinetics and variability of model-derived kinetic parameters is higher than desirable. This tracer should be suitable for use in receptor occupancy studies, particularly those that target high occupancy.