A NEW HUMAN (PSYCHO)PHARMACOLOGY TOOL - THE MULTIPLE ORGANS COINCIDENCES COUNTER (MOCC)

We describe a novel instrument which is capable of measuring the uptak e of radioligand in human organs in vivo with the administration of ve ry small doses of positron-emitting radioligands. This technique readi ly detects the displacement or reduced uptake of radioligand when a co mpetitive agonist or antagonist is administered. This system provides no tomographic information, but the small radioactive doses involved m ean that investigations can be repeated at regular interval, and that female volunteers can also participate. We administered [C-11]flumazen il, [C-11]diprenorphine, [C-11]meta-hydroxyephedrine (MHED) and [C-11] RTI 55 to healthy male volunteers and performed control, pre-loading a nd displacement experiments. These demonstrate the feasibility of usin g this technique to investigate benzodiazepine and opiate receptor occ upancy, as well as occupancy at dopamine, noradrenaline and serotonin (5-HT) re-uptake sites. This method is likely to be useful in pharmaco kinetic/pharmacodynamic experiments, in drug development and discovery and in the development of novel imaging radioligands.