A radiosynthetic method to prepare the nicotinic acetylcholine receptor radioligand (S)-5-[123I]iodo-3-(2-azetidinylmethoxy)pyridine, 5-1A, has been developed. The two-step sequence produced [123I]-5-1A in high radiochemical yield (52%), high radiochemical purity (98%), and high specific radioactivities (>8,500 mCi/μmol). Preliminary single photon emission computed tomography studies with [123I]-5-1A in baboon demonstrated the appropriate regional localization for a high-affinity nicotinic radioprobe (thalamus > frontal cortex > cerebellum). Pretreatment with cytisine blocked [123I]-5-1A uptake in all brain regions (78-59% reduction), demonstrating the specificity of the radiotracer.
- Nicotinic acetylcholine receptor