Synthesis and evaluation of 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-[11C]ethyl-1,3-dihydro-2H-benzimidazol-2-one as a brain ORL1 receptor imaging agent for positron emission tomography

1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-[C-11]ethyl-1,3-dihydro-2H-benzimidazol-2-one ([C-11]CPEB) was synthesized by [C-11]N-ethylation and evaluated as a potential brain OPL1 receptor imaging agent by positron emission tomography. The uptake of [C-11]CPEB in the mouse brain was 1.9% dose/g, 2 min post-injection, and gradually decreased with time. Receptor-specific binding was observed, however, the contribution of other receptors was observed and the non-specific binding of [C-11]CPEB was too high for imaging receptors in vivo. Therefore, [C-11]CPEB is not a suitable tracer for in vivo ORL1 receptor imaging. (C) 2002 Elsevier Science Inc. All rights reserved.