Kineticsof [nC]N,N- Dimethylphenylethylamine in Mice and Humans: Potential for Measurement of Brain MAO-B Activity

Carbon-11-labeled N,N-dimethylphenylethylamine ([11C]DMPEA) was synthesized by the reaction of N-methylphenylethylamine with [l1C]methyl iodide. This newly synthesized radiotracer was developed for the purpose of in vivo measurement of monoamine oxidase-B activity in the brain using a metabolic trapping method. Initially, biodistribution was investigated in mice. The rapid and high uptake of 11Cradioactivity in the brain was observed following intravenous injection of [11C]DMPEA, the peak of which was reached at 1 min, followed by a decrease at 1-5 min and slowly thereafter. The kinetics of [11C]DMPEA in the human brain were determined using positron emission tomography (PET) and showed that 11Cradioactivity increased gradually over 60 min following initial rapid uptake of 11C radioactivity, with basal ganglia and thalamus showing high accumulation. J NucÃ-Med 28:1006-1011,1987 MLLonoamine oxidase (MAO) is widely distributed throughout the body and catalyzes the oxidative deam-ination of a variety of monoamines ( 7). MAO has been classified into two main types: MAO-A and MAO-B. MAO-A deaminates serotonin (5-HT) and noradrena-line (NA) much better than phenylethylamine (PEA) or benzylamine, and is preferentially inhibited by clor-gyline, whereas, MAO-B prefers PEA and benzylamine as substrates and is preferentially inhibited by 1-de-prenyl (2-4). Alterations of MAO-B activity in the brain has been implicated in aging, Alzheimer's disease, Huntington's disease, alcoholism, suicides, and affective illness (5