Radiosynthesis and preliminary evaluation of 5-[123/125I]iodo-3-(2(S)-azetidinylmethoxy)pyridine: a radioligand for nicotinic acetylcholine receptors.
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.
Horti
A G
AG
Brain Imaging Center, National Institute on Drug Abuse, Baltimore, Maryland 21224, USA.
Koren
A O
AO
Lee
K S
KS
Mukhin
A G
AG
Vaupel
D B
DB
Kimes
A S
AS
Stratton
M
M
London
E D
ED
D000818:Animals; D001345:Autoradiography; D001384:Azetidines / Q000378:metabolism* / Q000493:pharmacokinetics; D001921:Brain / Q000378:metabolism; D005069:Evaluation Studies as Topic; D007457:Iodine Radioisotopes; D008297:Male; D051379:Mice; D015394:Molecular Structure; D011854:Radiochemistry; D011869:Radioligand Assay; D051381:Rats; D011916:Rats, Inbred F344; D011978:Receptors, Nicotinic / Q000378:metabolism*; D014018:Tissue Distribution; D015899:Tomography, Emission-Computed, Single-Photon
C104288:A 85380; D001384:Azetidines; D007457:Iodine Radioisotopes; D011978:Receptors, Nicotinic