Effects of aging on 5-HT _2AR binding: A HRRT PET study with and without partial volume corrections

Objective We explored whether prior findings of reduction in serotonin 2A receptor (5-HT _2AR) binding with age could be replicated and whether high resolution research tomography (HRRT) for positron emission tomography could compensate for partial volume effects in the presence of age-related brain atrophy, which has been a traditional concern for radioligand PET studies in the elderly. Methods We derived 5-HT _2AR nondisplaceable binding potentials (BP _ND) in frontal, temporal, anterior-cingulate, insula, caudate and putamen volumes of interest (VOIs) for 28 healthy subjects (mean ± SD age = 43.9 ± 17.0 years, range: 19-78 years) using HRRT. Partial volume correction (PVC) was performed in the VOI analysis. Results The 5-HT _2AR BP _NDs decreased with age, a relationship best described by an exponential-decay regression. The BP _NDs were found to be consistent before and after PVC, with an intra-class correlation coefficient of 0.84 and 95% confidence interval = 0.78-0.88. Conclusions These new findings update current knowledge, in that the aging process is not always uniform across the life span and suggest that PVC may not be necessary with HRRT in healthy subjects.