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Gao M, Mock BH, Hutchins GD, Zheng QH: Synthesis and initial PET imaging of new potential NK1 receptor radioligands 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-4-[11C] methyl-pip erazine and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl} -acetic acid [11C] methyl ester. Nucl Med Biol. 2005 Jul;32(5):543-52.
The NK (1) receptor radioligands 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-4-[(11) C] methyl-p iperazine ([(11) C] BMP, [(11) C]) and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl} -acetic acid [(11) C] methyl ester ([(11) C] BME, [(11) C]) were synthesized for evaluation as new potential PET imaging agents for brain NK (1) receptors. The new tracers [(11) C] BMP and [(11) C] BME were prepared by N-[(11) C] methylation and O-[(11) C] methylation of corresponding precursors 1-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine and {4-[2-(3,5-bis-trifluoromethyl-benzyloxy)-1-phenyl-ethyl]-piperazine-1-yl} -acetic acid using [(11) C] methyl triflate and isolated by solid-phase extraction (SPE) purification procedure with 40-55% radiochemical yields, decay corrected to end of bombardment, and a synthesis time of 15-20 min. The initial PET dynamic studies of the tracers [(11) C] and [(11) C] in rats were performed using an animal PET scanner, IndyPET-II, developed in our laboratory. The results show the tracer [(11) C] BMP had better uptake in the animal brain than the tracer [(11) C] BME and gave higher quality rat brain images. Blocking studies by intravenous coinjection of hot tracer [(11) C] BMP with cold drug BMP had no effect on [(11) C] BMP-PET rat brain imaging. Likewise, blocking studies by intravenous coinjection of hot tracer [(11) C] BME with cold drug BME also showed no effect on [(11) C] BME-PET rat brain imaging. These results suggest that the localization of [(11) C] BMP and [(11) C] BME in rat brain is mediated by nonspecific processes, and the visualization of [(11) C] BMP-PET and [(11) C] BME-PET on rat brain is related to nonspecific binding. |
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