Trenton Simmons, Brigham Young University
Psychology
Endogenous opioids are believed to modulate social sensitivity and aggression. The mu-opioid receptor gene in rhesus macaques has two common variants thought to be orthologous to human variants: C77G (CG) and C77C (CC). Based on previous studies, we predicted that rhesus macaques with the CG variant would exhibit higher rates of antisocial and aggressive behavior during social challenge. To test this hypothesis, we subjected mother-reared (MR) and nursery-reared (NR) subjects to an intruder challenge. 130 subjects were genotyped for the mu-opioid receptor gene variant. Behaviors were recorded after an unfamiliar intruder of the same sex and age was placed adjacent to the subjects’ home cage. CG, MR males received more non-contact aggression from group members than any other condition (p range<0.012), instigated more contact aggression than any other condition (p range<0.018), and received more contact aggression from the intruder than all other conditions except CC, NR males. In contrast to high rates of aggression, male, CG, MR subjects exhibited the lowest time in social affiliation when compared to all other genotype, sex or rearing conditions (p<0.026) except for CG, NR females. Our findings suggest that the mu-opioid receptor gene modulates aggression and antisocial behavior but only in the context of rearing and sex. These findings suggest one potential pathway for antisocial aggressive behavior development in men.