A test-retest (TRT) investigation of [11C]PHNO in human is required to further characterise [11C]PHNO. [11C] PHNO possesses very high affinity for the D3 receptor, and therefore most clinical studies are conducted at D3 occupancies >10%. As [11C]PHNO kinetics in the target brain regions are moderately slow, considerable mass carry over may be present on a 2nd PET scan conducted on the same day. In addition there appears to be a significant displaceable binding component in the cerebellum, which, if not accounted for, will lead to a bias in the quantification of specific [11C]PHNO binding. The aim of this study is therefore to examine the effects of [11C]PHNO mass carry-over and displaceable binding in the cerebellum, on the quantification of [11C]PHNO PET data.~This will be an open label, non-randomised [11C]PHNO PET study using healthy volunteers. Each volunteer will undergo 4 [11C]PHNO PET scans:~1st and 2nd scans; TRT on the same day with a minimal gap between [11C]PHNO injections to examine the effects of PHNO mass carry over, 3rd scan >1 week later to determine the true TRT variability and a 4th scan will follow a 15mg dose of aripiprazole (a D2/D3 compound which allows the highest clinically acceptable blockade of central D2/D3 receptors) and will examine the amount of displaceable binding in the cerebellum, a proposed reference tissue for [11C]PHNO.~The scan data will be quantified as regional volumes of distribution (VT).
This will be an open label, non-randomised [11C]PHNO PET study using healthy male volunteers. Each volunteer will undergo 4 [11C]PHNO PET scans to allow for further characterisation of this radioligand and examine the effects of [11C]PHNO mass carry-over and displaceable binding in the brain. This study aims to obtain data from 6 evaluable subjects.