It is noteworthy that mGluR5 regulates various mechanisms implicated in neurogenesis and synaptic maintenance, and the abnormal regulation of mGluR5 has been implicated in the pathophysiology of many neurological and psychiatric disorders, including pain, epilepsy, schizophrenia, drug addiction and Alzheimer’s disease [7]. This evidence concerns the gene GRM5 and early-onset autosomal dominant Alzheimer disease.