Synthesis and pharmacological characterization of a new PET ligand for the serotonin transporter: [11C]5-bromo-2-[2-(dimethylaminomethylphenylsulfanyl)]phenylamine ([11C]DAPA).
A new PET radioligand for the serotonin transporter (SERT), [11C]-5-bromo-2-[2-(dimethylaminomethylphenylsulfanyl)]phenylamine ([11C]DAPA (10), was synthesized and evaluated in vivo in rats and baboons. [11C]DAPA (10) was prepared from its monomethylamino precursor 8 by reaction with high specific activity [11C]methyl iodide. Radiochemical yield was 24 +/- 5% based on [11C]methyl iodide at end of bombardment (EOB, n = 10) and specific activity was 1,553 +/- 939 Ci/mmol at end of synthesis (EOS, n = 10). Binding assays indicated that [11C]DAPA displays high affinity (Ki 1.49 +/- 0.28 nM for hSERT) and good selectivity for the SERT in vitro. Biodistribution studies in rats indicated that [11C]DAPA enters into the brain readily and localizes in brain regions known to contain high concentrations of SERT, such as the thalamus, hypothalamus, frontal cortex and striatum. Moreover, such binding in SERT-rich regions of the brain are blocked by pretreatment with either the selective serotonin reuptake inhibitor (SSRI) citalopram and by the cold compound itself, demonstrating that [11C]DAPA binding in the rat brain is saturable and specific to SERT. Imaging experiments in baboons indicated that [11C]DAPA binding is consistent with the known distribution of SERT in the baboon brain, with highest levels of radioactivity detected in the midbrain and thalamus, intermediate levels in the hippocampus and striatum, and lower levels in the cortical regions. Pretreatment of the baboon with citalopram 10 min before radioactivity injection blocked the binding of [11C]DAPA in all brain regions that contain SERT. Kinetic analysis revealed that, in all brain regions examined, [11C]DAPA specific to nonspecific distribution volume ratios (V(3)") are higher than [11C](+)-McN 5652 and similar to [11C]DASB. In summary, [11C]DAPA appears to be a promising radioligand suitable for the visualization of SERT in vivo using PET.
Huang
Yiyun
Y
Department of Psychiatry, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA. hh285@columbia.edu
Hwang
Dah-Ren
DR
Zhu
Zhihong
Z
Bae
Sung-A
SA
Guo
Ningning
N
Sudo
Yasuhiko
Y
Kegeles
Lawrence S
LS
Laruelle
Marc
M
D000814:Aniline Compounds / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D015283:Citalopram / Q000008:administration & dosage; D005260:Female; D007553:Isotope Labeling / Q000379:methods; D008024:Ligands; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D010215:Papio; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050486:Serotonin Plasma Membrane Transport Proteins; D013440:Sulfides / Q000138:chemical synthesis* / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D014055:Tomography, Emission-Computed / Q000379:methods*
C473952:5-bromo-2-(2-(dimethylaminomethylphenylsulfanyl))phenylamine; D000814:Aniline Compounds; D002352:Carrier Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D019275:Radiopharmaceuticals; D050486:Serotonin Plasma Membrane Transport Proteins; C493232:Slc6a4 protein, rat; D013440:Sulfides; D015283:Citalopram