GRM5 and Alzheimer disease: The importance of mGluR5 (metabotropic glutamate receptor 5), NMDAR (N-methyl-d-aspartate receptor) and AMPAR (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor), three receptors that interact to regulate excitatory synaptic transmission, in AD has been reviewed [46].