Evaluation of radioiodinated (2S,αS)-2-(α-(2-iodophenoxy)benzyl)morpholine as a radioligand for imaging of norepinephrine transporter in the heart

Yasushi Kiyono, Taku Sugita, Masashi Ueda, Hidekazu Kawashima, Naoki Kanegawa, Yuji Kuge, Yasuhisa Fujibayashi, Hideo Saji

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Introduction: The norepinephrine transporter (NET) is located presynaptically on noradrenergic nerve terminals and plays a critical role in the regulation of the synaptic norepinephrine (NE) concentration via the reuptake of NE. Changes in NET have been recently reported in several cardiac failures. Therefore, a NET-specific radioligand is useful for in vivo assessment of changes in NET density in various cardiac disorders. Recently, we developed a radioiodinated reboxetine analogue, (2S,αS)-2-(α-(2-iodophenoxy)benzyl)morpholine ((S,S)-IPBM), for NET imaging. In the current study, we assessed the applicability of radioiodinated (S,S)-IPBM to NET imaging in the heart. Methods: The NET affinity and selectivity were measured from the ability to displace specific [3H]nisoxetine and (S,S)-[125I]IPBM binding to rat heart membrane, respectively. To evaluate the distribution of (S,S)-[125I]IPBM in vivo, biodistribution experiment was performed in rats. With the use of several monoamine transporter binding agents, pharmacological blocking experiments were performed in rats. Results: In vitro binding assays showed that the affinity of (S,S)-IPBM to NET was similar to those of the well-known NET-specific binding agents, nisoxetine and desipramine. Furthermore, (S,S)-[125I]IPBM binding was inhibited by nisoxetine and desipramine, but not by dopamine or serotonin transporter binding agents. These data indicated that (S,S)-IPBM had high affinity and selectivity for NET in vitro. Biodistribution studies in rats showed rapid and high uptake of (S,S)-[125I]IPBM by the heart and rapid clearance from the blood. The heart-to-blood ratio was 31.9 at 180 min after the injection. The administration of nisoxetine and desipramine decreased (S,S)-[125I]IPBM accumulation in the heart, but injection of fluoxetine and GBR12909 had little influence. Conclusions: Radioiodinated (S,S)-IPBM is a potential radioligand for NET imaging in the heart.

Original languageEnglish
Pages (from-to)213-218
Number of pages6
JournalNuclear Medicine and Biology
Issue number2
Publication statusPublished - Feb 2008
Externally publishedYes


  • (S,S)-IPBM
  • Heart
  • Norepinephrine transporter
  • Radioiodination
  • Sympathetic nervous function

ASJC Scopus subject areas

  • Molecular Medicine
  • Radiology Nuclear Medicine and imaging
  • Cancer Research


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