OPRM1 and Alzheimer disease: No effect was observed with administration of MOR antagonist on the generation of Aβ or amyloid plaque formation, and MOR antagonist was not able to reverse the learning and memory deficiency of the AD mouse model (Teng et al., 2010), although another group reported improved spatial memory retention in this transgenic AD mouse model with MOR antagonist treatment (Meilandt et al., 2008).