The synaptic density in the composite cortical VOI was positively associated with regional mGluR5 availability in the frontal (r = 0.607, p = 0.005), lateral temporal (r = 0.535, p = 0.015), medial temporal (r = 0.443, p = 0.048), and occipital lobes (r = 0.520, p = 0.019) and p posterior cingulate crus (r = 0.447, p = 0.033), and these associations were independent of global amyloid deposition. Here, GRM5 is linked to amyloidosis.