Synthesis and biodistribution of 2-[123I]iodomelatonin in normal mice

Melatonin demands that this hormone and its receptors be well understood. With this aim in mind, synthetic melatonin was radioiodinated with no-carrier-added (n.c.a.) sodium iodide-123 using in situ generated peracetic acid as oxidizing agent for electrophilic iodination at room temperature. The radiochemical yield was typically greater than 80% after 20 min reaction time especially when relatively small amounts of activities were used (⩽10 mCi). Biological evaluation was performed in normal mice. The distribution of the tracer did not reveal any specificity during the time frame studied. There was no significant retention in the whole brain.