Opiate effects on social behavior of juvenile dogs as a function of social deprivation

The relationship between opioids and social behavior was examined by administering morphine (an opioid agonist) and naloxone (an opioid antagonist) to juvenile dogs and measuring various social behaviors (e.g., tail wagging) in a large room. Drugs were administered following social deprivation and nondeprivation. It was hypothesized that morphine would ease effects of social deprivation while naloxone would result in behavior typical of untreated socially-deprived dogs. Social deprivation (24 hr) resulted in more contact with the experimenter and increased tail wagging relative to nondeprivation. Morphine (0.25 mg/kg) resulted in more contacts with the experimenter and entrances into the "experimenter's area" relative to vehicle injections. Further, morphine decreased and naloxone increased tail wagging in the dog's area and there was a significant social condition X drug interaction for that measure. Naloxone (0.25 mg/kg) increased wagging following nondeprivation while morphine decreased wagging following deprivation. These data support the hypotheses that social deprivation can increase social behaviors, and that social behavior is regulated by activity in brain opioid systems.