GRM4 and Alzheimer disease: Downregulation of Rims3 (regulating synaptic membrane exocytosis 3), Gabra6 (gamma-aminobutyric acid type A receptor subunit alpha6), Grm4 (glutamate metabotropic receptor 4) and the upregulation of PTK2B (Protein Tyrosine Kinase 2 Beta), NELL2 (Neural EGFL Like 2) in AD animals versus controls, suggest synaptic dysfunction in AD rats.