GRM5 and Alzheimer disease: Li et al. (2016) noted that both neurotransmission systems might undergo pathological changes in AD. In this study, we evaluated the in vivo changes in mGluR5 in APPswe/PS2 mice and observed that the uptake of 18F-FPEB in the AD group was considerably lower than that in the WT group, which is consistent with our previous work and a clinical study conducted by Mecca et al. (2020) (Lee et al., 2018). This reduced expression of mGluR5 indicated the diminished availability of binding sites for radiotracers since mGluR5 is a scaffold for Aβ oligomers and cellular prion proteins (Um et al., 2013).