Effects of age on dopamine transporters in healthy humans

Tc-99m-TRODAT-1 is a new radiopharmaceutical that selectively binds the dop amine transporters. This study characterized the effects of aging on its re gional cerebral distribution in healthy human volunteers, Methods: The samp le consisted of 27 men and 28 women with a mean age of 41.1 +/- 17.1 y (age range 18.7-73.8 y), Dynamic SPECT scans of the brain were obtained with a standardized acquisition and processing protocol on a triple-head camera, M ean counts per pixel were measured in multiple regions of interest within e ach basal ganglia. Regression analyses were used to relate the specific upt ake values at 3-4 h after administration to age. Both linear and nonlinear models of aging were tested. Results: The relative concentration of radioac tivity in most subregions of the basal ganglia decreased significantly with age (all P values < 0.0001), Nonlinear models of aging fit the data signif icantly better than a straight line, The rate of decline was significantly faster in young adults than in older volunteers (P < 0.001), The break-poin t age at which the rate of change slowed down and became more stable was 36 y old for the whole striatum and ranged from 32 to 44 y old depending on s ubregion, Conclusion: The effects of aging on central nervous system dopami ne transporters do not appear to be linear, Most effects seem to occur duri ng young adulthood before people reach their 40s, The distribution then app ears to remain relatively stable until late in life, The findings suggest t hat the adult life cycle is better characterized as a series of phases than as a continuum.