Characterization of the binding sites for 123I-ADAM and the relationship to the serotonin transporter in rat and mouse brains using quantitative autoradiography

Kun Ju Lin, Tzu Chen Yen, Shiaw Pyng Wey, Jeng Jong Hwang, Xin Xian Ye, Kai Yuan Tzen, Ying Kai Fu, Jin Chung Chen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


Imaging of serotonin transporter (SERT) in the central nervous system may provide an important tool to evaluate some psychiatric disorders. Recently, a novel 123I-labeled radiotracer, 2-((2-((dimethylamino)methyl)phenyl) thio)-5-iodophenylamine (123I-ADAM), has been developed that exhibited a high selectivity for SERT. The aim of this study was to characterize the biodistribution and specificity of 123I-ADAM to SERT using quantitative autoradiography in both control and neurotoxin-treated animals. Methods: 123I-ADAM (74 MBq) was injected intravenously into the mice to access its biodistribution in the brain via quantitative autoradiography. Further, rats with serotonin depleted by intraperitoneal injection of p-chloroamphetamine (PCA) were used to evaluate the specificity of 123I-ADAM to SERT. The levels of biogenic amines were then measured and correlated with quantitative 123I-ADAM labeling in control and PCA-treated rat brains. Results: The autoradiographic results showed that 123I-ADAM accumulated in SERT-rich brain areas after systemic injection, including the globus pallidus, thalamus, hypothalamus, substantia nigra, interpeduncular nucleus, amygdala, and raphe nucleus. The dorsal raphe nucleus had the highest initial uptake with a peak specific binding ratio (i.e., [target - cerebellum]/cerebellum) at 120 min after injection. 123I-ADAM uptake was dramatically decreased in the hippocampus, thalamus, amygdala, geniculate nuclei, hypothalamus, raphe nucleus, and substantia nigra in PCA-lesioned rats. The decrement in radioactivity was more prominent at higher dosages of PCA and was in parallel with the changes in amounts of serotonin and 5-hydroxyindoleacetic acid in the prefrontal cortex. Conclusion: This study demonstrates that regional distribution of 123I-ADAM radioactivity is similar to the SERT localization in both rat and mouse brains. We also validated that destruction on central serotonergic neurons after PCA treatment inhibits the uptake of 123I-ADAM in serotonin-rich brain regions. High specific binding to SERT in vivo makes 123I-ADAM an appropriate radiotracer for solitary studies of serotonin functions in living humans.

Original languageEnglish
Pages (from-to)673-681
Number of pages9
JournalJournal of Nuclear Medicine
Issue number4
StatePublished - Apr 2004


  • Biodistribution
  • Quantitative autoradiography
  • Serotonin transporter


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