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

This study investigates the rate of age-related dopamine D-2 receptor loss as determined by positron emission tomography (PET) and C-11-raclopride and compares it with D-2 loss previously estimated with F-18-N-methylspiroperidol (NMS). Dopamine D-2 receptors were measured with C-11-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 receptor loss per decade corresponded to 7.9% for the C-11-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).