CHAPTER 5 – The MOC Counter: A Pharmacological Tool for the in Vivo Measurement of Ligand Occupancy Indices in the Human Brain

The advent of computerized tomography of radioligands has resulted in the ability to investigate drug occupancy in tissues of interest and thus to provide a more direct pharmacokinetic measure of drug concentration in the target organs than the estimation of free drug in plasma. This chapter describes the development of a technique that has the potential to measure macroregional indices of drug delivery and occupancy using very low levels of radiation ( 11 c]flumazenil (a benzodiazepine site marker), [ 11 C]diprenorphine (an opiate receptor marker), [ 11 C]RTI 55 (a dopamine and serotonin reuptake site marker), and [ 11 C]WAY 100635 are also discussed as examples in the chapter.