Age-related reduction of extrastriatal dopamine D 2 receptor measured by PET

Abstract

Although the aging effect of dopamine D 2 receptor in the striatum is well-documented, the effect of age on the extrastriatal dopamine D 2 receptor has not been fully examined. Since the density of extrastriatal dopamine D 2 receptor is very low, suitable ligands are limited. In this study, we used [11C]FLB 457 to quantify the extrastriatal dopamine D 2 receptor in the living human brain. Twenty-seven healthy male subjects aged from 21 to 82 years participated in the positron emission tomography study. Extrastriatal [ 11C]FLB 457 binding was quantified with a reference tissue model using cerebellum as a reference region. Binding potentials corresponding to Bmax /Kd were used to evaluate age-related change. We found age-related decreases of D 2 receptor binding in all measured extrastriatal regions. The decrease of D 2 receptor binding was 13.8% per decade in frontal cortex, 12.0% in temporal cortex, 13.4% in parietal cortex, 12.4% in occipital cortex, 12.2% in hippocampus, and 4.8% in thalamus. These findings suggest that the amounts of D 2 receptor declines in all brain regions as part of the normal aging process.