GRM5 and Alzheimer disease: mGluR5 antagonists have been proposed as a treatment for AD (Kumar et al. 2015; Sokol et al. 2011), largely based on research from rodent models, e.g., where knockout of mGluR5 (Hamilton et al. 2014) or negative allosteric modulation of mGluR5 (Abd-Elrahman et al. 2020) can reduce amyloid pathology and protect cognition.