Determination of in vivo Bmax and Kd for [11C]GR103545, an agonist PET tracer for kappa opioid receptors: A study in nonhuman primates

The kappa opioid receptors (KOR) are involved in mood disorders and addictive conditions. In vivo imaging studies of this receptor in humans have not been reported due to the lack of a selective ligand. We employed a recently developed selective KOR agonist tracer, [ 11 C]GR103545, and performed a study in rhesus monkeys to estimate the in vivo receptor concentration ( B max ) and dissociation equilibrium constant ( K d ).