[11C]Yohimbine PET Study of alpha2-AR

Each subject will receive an intravenous (IV) bolus injection of \[11C\]Yohimbine at a dose of 370 MegaBecquerel (MBq) ± 10% with concomitant arterial blood sampling. The distribution of \[11C\]Yohimbine in brain will be measured by dynamic PET scans obtained from the time of injection for up to 90 minutes along with measurement of the tracer input function with arterial samples for intact tracer and metabolites to establish the total and regional compartmental kinetics of \[11C\]Yohimbine.

"Part B1 : Test Retest Variability will be assessed on percent difference in the binding potential following \[11C\]Yohimbine PET scan (IV bolus injection of \[11C\]Yohimbine at a dose of 370 MBq ± 10%) obtained at least 1 week after \[11C\]Yohimbine PET scan of part A.~Part B2 : Occupancy of alpha2-adrenergic receptors in brain by clonidine will be evaluated by comparing the binding potential of \[11C\]Yohimbine (IV bolus injection of \[11C\]Yohimbine at a dose of 370 MBq ± 10%) after single oral dose of clonidine (0,15mg) to the binding potential of \[11C\]Yohimbine obtained at baseline (part A)."