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Clinical Investigations |
1 Positron Medical Center, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan
2 Proton Medical Research Center, University of Tsukuba, Ibaragi, Japan
3 Department of Radiology, Jikei University School of Medicine, Tokyo, Japan
Adenosine is an endogenous modulator of synaptic functions in the central nervous system. To investigate the physiologic and pathologic roles of the adenosine receptors in the human brain, PET is a powerful in vivo technique. In this study, we quantitatively evaluated the distribution of a major subtype A1 adenosine receptor in the human brain by PET with a newly developed radioligand, 8-dicyclopropylmethyl-1-11C-methyl-3-propylxanthine (11C-MPDX). Methods: In 5 healthy volunteers, after PET measurement of the regional cerebral blood flow (rCBF) with 15O-H2O, a 60-min PET scan with 11C-MPDX was performed. The distribution volume (DV) of 11C-MPDX was quantitatively evaluated by Logans graphical analysis. Results: 11C-MPDX was taken up at a high level, reaching a peak at 22.5 min, followed by a rapid decrease. The unchanged form of 11C-MPDX in plasma was 75% at 60 min after injection. The DV of 11C-MPDX was large in the striatum and thalamus, moderate in the cerebral cortices and pons, and small in the cerebellum. The distribution pattern of 11C-MPDX in the brain was coincident with that of adenosine A1 receptors in vitro, reported previously, but discretely different from that of rCBF. Conclusion: 11C-MPDX PET has the potential for mapping adenosine A1 receptors in the human brain.
Key Words: 8-dicyclopropylmethyl-1-11C-methyl-3-propylxanthine adenosine A1 receptor brain PET
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