EFFECTS OF OPIOID RECEPTOR BLOCKADE ON THE SOCIAL-BEHAVIOR OF RHESUS-MONKEYS LIVING IN LARGE FAMILY GROUPS

Rhesus monkeys of 9 weeks, 48 weeks, 100 weeks, 150 weeks of age (youn g subjects), or mature parous females that were not lactating were giv en acute single doses of the opioid antagonist naloxone (0.5 mg/kg) an d vehicle on different days and observed in their familial social grou ps. Naloxone increased the occurrence of affiliative behaviors. Young subjects spent more time in contact with their mothers but showed no c hanges in social grooming. Maternal contact was actively sought throug h contact vocalizations, decreasing proximity, and, for the youngest i nfants, increased attempts to suckle. Mature females made more solicit ations for grooming and received more grooming from their companions. These results are interpreted in terms of naloxone blocking the positi ve affect arising from social contact and thus causing subjects to see k further affiliative comfort. (C) 1995 John Wiley and Sons, Inc.