11C-labelling of indolealkylamine alkaloids and the comparative study of their tissue distributions

Abstract

Five indolealkylamines (N,N-dimethyltryptamine, N-methyltryptamine, bufotenine, O-methylbufotenine, N,N,N-trimethyltryptamine iodide) were labeled with ¹¹C by use of ¹¹CH₃I. The labeled compounds were synthesized with a radiochemical yield of 2–50% (based on trapped ¹¹CH₃I) in 20–35 min with radiochemical purities of more than 92%. The tissue distributions of these labeled compounds were investigated in rats. In all cases, the accumulations in the liver, lung and small intestine were high. [¹¹C]DMT and [¹¹C]OMB also accumulated to a large extent in the brain, where their accumulation was retained. Brain uptake of three other radiopharmaceuticals was low. [¹¹C]DMT is the radiopharmaceutical of choice for the study of the serotonin action mechanism in the brain, because it has the highest radiochemical yield and the highest brain uptake of these ¹¹C-labeled compounds.