title: Variation at the mu-opioid receptor gene (OPRM1) influences attachment behavior in infant primates.
abstract: In a variety of species, development of attachment to a caregiver is crucial for infant survival and partly mediated by the endogenous opioids. Functional mu-opioid receptor gene polymorphisms are present in humans (OPRM1 A118G) and rhesus macaques (OPRM1 C77G). We hypothesized that rhesus infants carrying a gain-of-function OPRM1 77G allele would experience increased reward during maternal contact and would, therefore, display increased measures of attachment. We collected behavioral data from rhesus macaques (n = 97) during early infancy and at 6 months of age, across four cycles of maternal separation (4 days) and reunion (3 days). Animals were genotyped for the OPRM1 C77G polymorphism, and the effects of this allele on attachment-related behaviors were analyzed. Infants carrying the G allele exhibited higher levels of attachment behavior during early infancy. During prolonged periods of maternal separation, although infant macaques homozygous for the C allele exhibited decreases in their levels of distress vocalization with repeated separation, this response persisted in G allele carriers. The OPRM1 77G allele also affected social preference during reunion. C/G infants spent increasing amounts of time in social contact with their mothers as a function of repeated separation and were less likely to interact with other individuals in the social group, a pattern not observed among infants with the C/C genotype. These findings suggest a role for OPRM1 variation in the expression of attachment behavior in human subjects, especially as a function of separation from the caregiver.
authors: Laboratory of Clinical and Translational Studies, National Institutes of Health/National Institute on Alcohol Abuse and Alcoholism, Bethesda, MD 20892, USA.
authors: Christina S
authors: CS
authors: Barr
authors: Melanie L
authors: ML
authors: Schwandt
authors: Stephen G
authors: SG
authors: Lindell
authors: J Dee
authors: JD
authors: Higley
authors: Dario
authors: D
authors: Maestripieri
authors: David
authors: D
authors: Goldman
authors: Stephen J
authors: SJ
authors: Suomi
authors: Markus
authors: M
authors: Heilig
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D005260:Female; D005838:Genotype; D006801:Humans; D008253:Macaca mulatta / Q000378:metabolism* / Q000523:psychology*; D008297:Male; D023421:Models, Animal; D009035:Mothers; D009769:Object Attachment; D011110:Polymorphism, Genetic / Q000235:genetics*; D017450:Receptors, Opioid, mu / Q000235:genetics / Q000378:metabolism*
chemical_list: D017450:Receptors, Opioid, mu