Radiosynthesis and preliminary evaluation of 5-[123/125I]iodo-3-(2(S)-azetidinylmethoxy)pyridine: a radioligand for nicotinic acetylcholine receptors

Nucl Med Biol. 1999 Feb;26(2):175-82. doi: 10.1016/s0969-8051(98)00086-9.


The radiochemical syntheses of 5-[125I]iodo-3-(2(S)-azetidinylmethoxy)pyridine (5-[125I]-iodo-A-85380, [125I]1) and 5-[123I]-iodo-A-85380, [123I]1, were accomplished by radioiodination of 5-trimethylstannyl-3-((1-tert-butoxycarbonyl-2(S)-azetidinyl)metho xy)pyridine, 2, followed by acidic deprotection. Average radiochemical yields of [125I]1 and [123I]1 were 40-55%; and the average specific radioactivities were 1,700 and 7,000 mCi/mumol, respectively. Binding affinities of [125I]1 and [123I]1 in vitro (rat brain membranes) were each characterized by a Kd value of 11 pM. Preliminary in vivo assay and ex vivo autoradiography of mouse brain indicated that [125I]1 selectively labels nicotinic acetylcholine receptors (nAChRs) with very high affinity and specificity. These studies suggest that [123I]1 may be useful as a radioligand for single photon emission computed tomography (SPECT) imaging of nAChRs.

MeSH terms

  • Animals
  • Autoradiography
  • Azetidines / metabolism*
  • Azetidines / pharmacokinetics
  • Brain / metabolism
  • Evaluation Studies as Topic
  • Iodine Radioisotopes
  • Male
  • Mice
  • Molecular Structure
  • Radiochemistry
  • Radioligand Assay
  • Rats
  • Rats, Inbred F344
  • Receptors, Nicotinic / metabolism*
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon


  • A 85380
  • Azetidines
  • Iodine Radioisotopes
  • Receptors, Nicotinic