文摘
Purpose Dopamine D2/3 receptors (D2/3Rs) have two affinity states for endogenous dopamine, referred to as high-affinity state (D2/3 HIGH), which has a high affinity for endogenous dopamine, and low-affinity state (D2/3 LOW). The density of D2/3 HIGH can be measured with (R)-2-11CH3O-N-n-propylnorapomorphine ([11C]MNPA), while total density of D2/3 HIGH and D2/3 LOW (D2/3Rs) can be measured with [11C]raclopride using positron emission tomography (PET). Thus, the ratio of the binding potential (BP) of [11C]MNPA to that of [11C]raclopride ([11C]MNPA/[11C]raclopride) may reflect the proportion of the density of D2/3 HIGH to that of D2/3Rs. In the caudate and putamen, [11C]MNPA/[11C]raclopride reflects the proportion of the density of D2 HIGH to that of D2Rs. To evaluate the reliability of the PET paradigm with [11C]MNPA and [11C]raclopride, we investigated the test-retest reproducibility of non-displaceable BP (BP ND) measured with [11C]MNPA and of [11C]MNPA/[11C]raclopride in healthy humans. Methods Eleven healthy male volunteers underwent two sets of PET studies on separate days that each included [11C]MNPA and [11C]raclopride scans. BP ND values in the caudate and putamen were calculated. Test-retest reproducibility of BP ND of [11C]MNPA and [11C]MNPA/[11C]raclopride was assessed by intra-subject variability (absolute variability) and test-retest reliability (intraclass correlation coefficient: ICC). Results The absolute variability of [11C]MNPA BP ND was 5.30?±-.96?% and 12.3?±-.95?% and the ICC values of [11C]MNPA BP ND were 0.72 and 0.82 in the caudate and putamen, respectively. The absolute variability of [11C]MNPA/[11C]raclopride was 6.11?±-.68?% and 11.60?±-.70?% and the ICC values of [11C]MNPA/[11C]raclopride were 0.79 and 0.80 in the caudate and putamen, respectively. Conclusion In the present preliminary study, the test-retest reproducibility of BP ND of [11C]MNPA and of [11C]MNPA/[11C]raclopride was reliable in the caudate and putamen.