Effect of endogenous dopamine on extrastriatal [C-11]FLB 457 binding measured by PET

Central dopaminergic systems are known to be implicated in the pathophysiol ogy of schizophrenia and recent in vivo dopamine receptor imaging studies h ave focused on the measurement of extrastriatal dopamine receptor. However, there are only a limited number of ligands that can measure the low-densit y D, receptor in extrastriatal regions and their sensitivity to endogenous dopamine in extrastriatal regions has not yet been fully examined. In this study, the effect of endogenous dopamine on the extrastriatal binding of [C -11]FLB 457 was examined in the rhesus monkey after facilitation with 1 mg/ kg of methamphetamine (MAP) and was compared with the effect on the striata l binding of [C-11]raclopride. The indices of receptor binding were obtaine d by four methods using cerebellum as a reference region. The bindings of [ C-11]FLB 457 in the frontal cortex, temporal cortex, and thalamus were not significantly changed after MAP treatment, while the striatal binding of [C -11]raclopride was decreased by more than 20%. These results suggest that [ C-11]FLB 457 is not sensitive to endogenous dopamine in the extrastriatal r egions of rhesus monkeys, despite a sufficient dose of MAP to decrease the binding of [C-11]raclopride in the striatum. (C) 2001 Wiley-Liss, Inc.