Measuring age-related changes in dopamine D 2 receptors with 11C-raclopride and 18F- N-methylspiroperidol

Abstract

This study investigates the rate of age-related dopamine D 2 receptor loss as determined by positron emission tomography (PET) and 11C-raclopride and compares it with D 2 loss previously estimated with 18F- N-methylspiroperidol (NMS). Dopamine D 2 receptors were measured with 11C-raclopride in 24 healthy volunteers (24–73 years of age) using the ratio of the distribution volume in striatum to that in cerebellum ( B max K d +1 ). The results were compared with those obtained in 20 healthy male volunteers (20–49 years of age) in whom D 2 receptors were measured with NMS using the ratio index (slope of the striatum-to-cerebellum ratio as a function of time). Findings of correlational analysis between age and dopamine D 2 receptor availability were significant for both ligands. Estimates of dopamine D 2 receptors loss per decade corresponded to 7.9% for the 11C-raclopride study and 7.8% for the NMS study. Both ligands documented significant age-related decreases in dopamine D 2 receptors that occurred relatively early in life (40 years of age).