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Synthesis and Evaluation of [11C]FR194921 as a Nonxanthine-Type PET Tracer for Adenosine A1 Receptors in the Brain

Synthesis and Evaluation of [11C]FR194921 as a Nonxanthine-Type PET Tracer for Adenosine A1 Receptors in the Brain

Takahiro Matsuya, Hiroyuki Takamatsu, Yoshihiro Murakami, Akihiro Noda, Rikiya Ichise, Yuji Awaga, Shintaro Nishimura

Nucl Med Biol. 2005 Nov;32(8):837-44.

PMID: 16253808

Abstract:

This report describes the synthesis of [11C]2-(1-methyl-4-piperidinyl)-6-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)-3(2H)-pyridazinone ([11C]FR194921), a highly selective, nonxanthine-type adenosine A(1) receptor antagonist, used in brain imaging in rats and conscious monkeys as a potential novel PET tracer. [11C]FR194921 was successfully synthesized in 19 min after [11C]CH3I formation. The radiochemical yield was 38+/-3%; and radioactivity was 4.1+/-0.4 GBq, calculated from end of synthesis; radiochemical purity was higher than 99%; and the specific radioactivity was 25.0+/-8.1 GBq micromol(-1) (n=5). In a rat experiment, the distribution of [11C]FR194921 was higher in the hippocampus, striatum and cerebellum regions. This accumulation was significantly decreased by approximately 50% by pretreatment with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist, which indicated specific binding of the radioligand to adenosine A1 receptors. In conscious monkey PET experiments, [11C]FR194921 accumulated in several regions of the brain, especially in the occipital cortex, thalamus and striatum. These results suggest that [11C]FR194921 can be used as an agent for imaging adenosine A1 receptors in vivo by positron emission tomography (PET).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP202646808	FR194921		202646-80-8	Price

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