Biodistribution of [18f] SR144385 and [18f] SR147963: selective radioligands for positron emission tomographic studies of brain cannabinoid receptors

ABSTRACT. [(18)F] SR144385 and [(18)F] SR147963 were synthesized in a multistep reaction in which fluorine-18 was introduced by nucleophilic halogen displacement on a bromo precursor. The fluorine-18-labeled intermediate was deprotected and coupled with the appropriate alkyl amine to give the final products. Both radioligands had appropriate regional brain distribution for cannabinoid receptors with a target to nontarget ratio of 1.7 for [(18)F] SR147963 and 2.5 for [(18)F] SR144385 at 60 and 90 min postinjection, respectively. The uptake of both tracers was blocked with a 1 mg/kg dose of SR141716A.