Carbon-11-FLB 457: a radioligand for extrastriatal D2 dopamine receptors.
D2 dopamine receptors in extrastriatal brain regions are of central interest for research in schizophrenia and antipsychotic drugs. This article reports the development of [11C]FLB 457 for PET examination of extrastriatal D2 dopamine receptors.


METHODS
Carbon-11-FLB 457 was prepared by O-methylation of FLB 604 (2-hydroxy precursor) with [11C]methyl iodide. Total radiochemical yield was 25%-35% within a total synthesis time of 30 min. The specific radioactivity at the end of synthesis was about 1300 Ci/mmole (48 GBq/mumole).


RESULTS
FLB 457 bound with high affinity to D2 and D3 dopamine receptors, whereas binding to other putative central receptors was negligible. PET studies in Cynomolgus monkeys demonstrated 15 times higher accumulation of radioactivity in the striatum than in the cerebellum after 60 min. Uptake in the thalamus and neocortex, extrastriatal regions with a low density of D2 dopamine receptors, was, respectively, 4 and 2.5 times higher than in the cerebellum. Radioactivity was displaced by raclopride and haloperidol which confirms the selectivity and reversibility of [11C]FLB 457 binding to D2 dopamine receptors in vivo in the striatum, thalamus and neocortex.


CONCLUSIONS
Carbon-11-FLB 457 should be a useful PET ligand for quantitative examination of D2 dopamine receptors in extrastriatal regions in the human brain.
Halldin
C
C
Department of Clinical Neuroscience, Karolinska Institute, Stockholm, Sweden.
Farde
L
L
Högberg
T
T
Mohell
N
N
Hall
H
H
Suhara
T
T
Karlsson
P
P
Nakashima
Y
Y
Swahn
C G
CG
D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D018492:Dopamine Antagonists / Q000493:pharmacokinetics; D008252:Macaca fascicularis; D008297:Male; D011759:Pyrrolidines / Q000493:pharmacokinetics; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D012457:Salicylamides / Q000493:pharmacokinetics; D014055:Tomography, Emission-Computed
D002250:Carbon Radioisotopes; D018492:Dopamine Antagonists; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; D012457:Salicylamides; C065065:FLB 457