In Vivo and In Vitro Imaging of I2 Imidazoline Receptors in the Monkey Brain

I-2 imidazoline receptors (I(2)Rs) are associated with depression, Alzheimer's disease, and Huntington's disease. However, in vivo imaging of I(2)Rs in the monkey brain has not been reported until now. We performed in vitro and in vivo imaging of (I(2)Rs) in the monkey brain using C-11-labeled 2-(3-fluoro-4-tolyl)-4,5-dihydro-1H-imidazole ([C-11]FTIMD) which has high and selective affinity of I(2)Rs. In an auto-radiography (ARG) study, the distribution pattern of [C-11]FTIMD in the monkey brain was similar to that of [H-3] idazoxan binging to I(2)Rs in the human brain, which was previously described. The specific binding of [C-11]FTIMD accounted for > 97% of total binding in brain regions existing I(2)Rs. In positron emission tomography (PET) studies, the radioactivity was accumulated in brain regions existing I(2)Rs ligand BU224, the accumulated radioactivity was decreased to approximately 66%-75% of the baseline measurement at 15-45 min after injection of [C-11]FTIMD. These results suggest that [C-11]FTIMD shows the specific-binging to I(2)Rs in the monkey brain as depicted by PET and ARG. We performed the first in vivo imaging of I(2)Rs using [C-11]FTIMD in the monkey brain. Synapse 65: 452-455, 2011. (C)2010 Wiley-Liss, Inc.