CSF 5-HIAA and aggression in female macaque monkeys: species and interindividual differences

• Published in: Psychopharmacology Vol. 146; no. 4; pp. 440 - 446
• Main Authors: Westergaard, G C, Suomi, S J, Higley, J D, Mehlman, P T
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01-10-1999
• Subjects: 5-Hydroxyindoleacetic acid; Aggression; Aggression - physiology; Animals; Biomarkers - cerebrospinal fluid; Dominance; Female; Females; Hydroxyindoleacetic Acid - cerebrospinal fluid; Impulsive behavior; Individuality; Macaca; Macaca mulatta; Macaca nemestrina; Medical treatment; Serotonin; Social Dominance; Species; Species Specificity; Wounding
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/PL00005489

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 across primates by making simultaneous comparisons between and within closely-related species.
We tested three hypotheses. First, that female rhesus macaques would have lower CSF 5-HIAA concentrations and be more aggressive than would female pigtailed macaques. Second, that females of both macaque species would exhibit an inverse relationship between interindividual differences in CSF 5-HIAA concentrations and rates of severe aggression. Third, that subjects with high CSF 5-HIAA concentrations would be higher in social dominance within their respective groups than would subjects with low CSF 5-HIAA concentrations.
We obtained CSF samples from 61 individually housed female primates of two closely related species: rhesus macaques (Macaca mulatta) and pigtailed macaques (Macaca nemestrina). We later placed subjects in unisex social groups, and correlated interindividual differences in CSF 5-HIAA with aggression, wounding, and acquisition of 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, as species that show relatively high rates of severe aggression also tend to have low concentrations of CSF 5-HIAA. 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.