Decreased 5-HT_1A binding in mild Alzheimer's disease-A positron emission tomography study

Decreased 5-HT_1A receptor binding has been associated with Alzheimer's disease (AD) and interpreted as a consequence of neuron loss. The purpose of the present study was to compare [¹¹ C]WAY100635 binding to the 5-HT_1A receptor in the hippocampus, entorhinal cortex, amygdala and pericalcarine cortex in mild AD patients and elderly controls. AD patients (n = 7) and elderly control subjects (n = 8) were examined with positron emission tomography (PET) and [¹¹ C]WAY100635. PET data acquisition was performed with an ECAT EXACT HR system. Wavelet-aided parametric images of nondisplaceable binding potential (BP_ND ) were generated using Logan's graphical analysis with cerebellum as the reference region. Correction for partial volume effects was performed with the Müller-Gärtner method. Regions of interest (ROIs) were applied to the individual parametric images, and the regional BP_ND was calculated as the average parametric voxel value within each ROI. In addition to comparisons between subject groups, correlations between BP_ND values and scores on the Mini-Mental State Examination, Disability Assessment for Dementia (DAD), and Neuropsychiatric Inventory were expressed by Pearson correlation coefficients. Mean regional BP_ND was lower in AD patients than in control subjects, and the difference was statistically significant for the hippocampus, entorhinal cortex, and amygdala. A statistically significant correlation was obtained between hippocampal BP_ND values and DAD scores. The results of the present study corroborate and extend previous findings of decreased 5-HT_1A binding in AD and strengthen the support for 5-HT_1A receptor PET as a tool for the assessment of neurodegenerative changes in mild AD.