Association between human gray matter metabotropic glutamate receptor-5 availability in vivo and white matter properties: a [11C]ABP688 PET and diffusion tensor imaging study

Excitatory corticofugal projections in the subcortical white matter (WM) convey signals arising from local neuronal activity in the gray matter (GM). We hypothesized that metabotropic glutamate receptor-5 (mGluR5) availability in GM, as a surrogate marker for local glutamatergic neuronal activity, correlates with WM properties in healthy brain. We examined the relationship in healthy individuals between GM mGluR5 availability measured in vivo using [ 11 C]ABP688 positron emission tomography (PET) and WM properties measured as fractional anisotropy (FA) using diffusion tensor imaging (DTI). Twenty-three healthy volunteers underwent this multimodal imaging. We calculated mGluR5 availability, [ 11 C]ABP688 binding potential (BP ND ), using the simplified reference tissue model, and generated DTI FA maps using FMRIB’s Diffusion Toolbox (FDT) along with Tract-Based Spatial Statistics (TBSS). To investigate the relationship between mGluR5 availability and FA, we performed voxel-wise and region of interest (ROI)-based analyses. The voxel-wise analysis showed significant positive correlations between the whole cerebral GM [ 11 C]ABP688 BP ND and the FA in widespread WM regions including the corpus callosum body, internal capsule, and corona radiata (FWE corrected p