[123I] beta-CIT, a tracer for dopamine and serotonin re-uptake sites: preparation and preliminary SPECT studies in humans.

beta-CIT (2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane) is a new ligand that has a high affinity to dopamine and serotonin re-uptake sites. [123I] beta-CIT was prepared by reacting the corresponding trimethylstannyl precursor with no-carrier-added 123I. Iodogen was used as an oxidizing agent. The labeling mixture was purified by filtration through a mini-column. The purity of the product was confirmed by analytical HPLC. The total radiochemical yield was 67 +/- 5%. The radiochemical purity was > 95% and the specific activity was > 107 GBq/mol (> 2900 Ci/mmol). The final product was confirmed to be free of endotoxins before intravenous administration. Two healthy male volunteers were injected iv with 120-160 MBq of [123I] beta-CIT and scanned with a 3-head gamma-camera (Siemens MultiSPECT3). Dynamic SPECT scans were performed for up to 2 hours. There was a high accumulation of radioactivity in the striatum and in the thalamus, and some in the medial prefrontal area. Thus, we have developed an easy method to prepare [123I] beta-CIT with a high specific radioactivity and in a sufficient radiochemical yield. Specific [123I] beta-CIT binding in striatal and thalamic regions was demonstrated in humans. [123I] beta-CIT is a potential marker of the dopamine and serotonin transporters and can be used to study the pathophysiology of Parkinson's disease, as well as neuropsychiatric disorders.