Kinetics of [11C]N, N-dimethylphenylethylamine in the brain

Carbon-11-labelled N, N-dimethylphenylethylamine ([11C] DMPEA) was synthesized by the reaction of N-methylphenylethylamine with ([11C] methyliodide. 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 11C radioactivity 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 11C radioactivity at 60 min following i. v. injection of [11C] DMPEA was decreased in a dose related manner by the pretreatment of 1-deprenyl but not decreased by clorgyline. The results suggest that MAO-B activity in the mouse brain can be estimated by [11C] DMPEA in vivo. The kinetics of [11C] DMPEA in the human brain were determined using positron emission tomography and showed that 11C radioactivity increased gradually over 60 min following initial rapid uptake of 11C radioactivity, with basal ganglia and thalamus showing high accumulation. The results suggest that the distribution of [11C] DMPEA may reflect the regional MAO-B activity in the human brain, but [11C] DMPEA needs to be modified for the measurement of MAO-B activity in the human brain because MAO-B activity in the human brain seems to be much higher than that in the mouse brain. (author)