479. CSF 5-HIAA and aggression in primates: species and interindividual differences

Abstract

While the relationship among CSF 5-HIAA, impulsivity, and aggression is well-characterized in males, its investigation in females is limited, and no studies have assessed its generalizability by making simultaneous comparisons between and within closely-related species. In this research we tested hypotheses that (1) female rhesus macaques would have lower CSF 5-HIAA concentrations and be more aggressive than would female pigtailed macaques; (2) females of both macaque species would exhibit an inverse relationship between interindividual differences in CSF 5-HIAA concentrations and rates of severe aggression; and (3) subjects with high CSF 5-HIAA concentrations would be higher in social dominance than would subjects with low CSF 5-HIAA concentrations. We obtained CSF samples from 61 female rhesus and pigtailed macaques and then correlated interindividual differences in CSF 5-HIAA with aggression, wounding, and social dominance rank. Between-species analyses indicated higher CSF 5-HIAA concentrations in pigtailed macaques, and higher rates of high-intensity aggression, escalated aggression, and wounds requiring medical treatment in rhesus macaques. Within-species analyses indicated that interindividual differences in CSF 5-HIAA concentrations were inversely correlated with escalated aggression and positively correlated with social dominance rank. These findings show that agonistic and social differences between closely-related species are correlated with CNS serotonin activity. We conclude that serotonergic functioning plays an important role in controlling impulses that regulate severe aggression and social dominance relationships in both male and female primates, and that between-species differences in agonistic temperament can be predicted by species typical CNS serotonin functioning.