P.3.23 Molecular imaging of early visual cortex by combining pet and fMRI

Abstract

Animal models revealed that the serotonin-1A (5-HT1A) receptor modulates gray matter structure. However, there is a lack of evidence showing the relationship between 5-HT1A receptor concentration and gray matter in the human brain in vivo. Here, to demonstrate an association between the 5-HT1A receptor binding potential, an index for receptor concentration, and the local gray matter volume (GMV), an index for gray matter structure, we measured 35 healthy subjects with both positron emission tomography (PET) and structural magnetic resonance imaging (MRI). We found that regional heteroreceptor binding was positively associated with GMV in distinctive brain regions such as the hippocampi and the temporal cortices in both hemispheres (R2 values ranged from 0.308 to 0.503, p < 0.05 cluster-level FDR-corrected). Furthermore, autoreceptor binding in the midbrain raphe region was positively associated with GMV in forebrain projection sites (R2 = 0.656, p = 0.001). We also observed a broad range between 5-HT1A receptor binding and GMV. Given the congruence of altered 5-HT1A receptor concentrations and GMV reduction in depression or Alzheimer's disease as reported by numerous studies, these results might provide new insights towards understanding the mechanisms behind GMV alterations observed in these brain disorders.