[11C]RO-5011232

This open label, non-randomized, parallel group study will evaluate [11C]-RO5011232 as radiotracer for brain mGlu5 receptor occupancy and investigate the binding of RO49917523 to human mGlu5 brain receptor at steady-state in healthy volunteers. In Parts I, II and III, positron emission tomography (PET) assessments of specific uptake of the radiotracer and whole body dosimetry will be made after intravenous injection of [11C]-RO5011232. In Part IV, subjects will receive RO4917523 orally daily for 14 days while receiving three single intravenous bolus injections of [11C]-RO5011232. The anticipated time on study treatment is up to 4 weeks.