GRIN1 and schizophrenia: Grin1 hypomorphic mice, which express 5–10% of Grin1 compared to wild-type, show increased locomotor activity and stereotypy [22,23], impaired social [23,24] and sexual behaviors [22], deficits in nest building [22], and decreased PPI [24], all of which are considered to be behavioral abnormalities relevant to schizophrenia [25].