OPIATE SYSTEMS IN MOTHER AND INFANT PRIMATES COORDINATE INTIMATE CONTACT DURING REUNION

In humans, and non-human primates, reunion following a separation resu lts in a positive emotional stare, and an increase in affiliative beha viors. To examine the role of opiate systems, in mothers and infants i n mediating reunion behavior, morphine and naltrexone were administere d after a brief separation. Infants administered morphine (0.1 mg/kg I M) showed a significant reduction in clinging and girning, a vocalizat ion emitted during close physical contact. Naltrexone (5 mg/kg IM) had opposite effects. When administered to mothers, again morphine decrea sed and naltrexone increased clinging. Morphine administered to mother s had a more transient behavioral effect which could not be accounted for by lower morphine blood levels. These results demonstrate that dur ing reunion, the amount of intimate contact between a mother and her i nfant is regulated by the reciprocal activation of their opiate system s. This activation of opiate systems may reinforce the infant's need f or attachment and the mother's role in care giving.