Differing concentrations of corticotropin-releasing factor and oxytocin in the cerebrospinal fluid of bonnet and pigtail macaques.

The two neuropeptides corticotropin-releasing-factor (CRF) and oxytocin (OT) may produce opposing behavioral effects - elevations of the former have been associated with anxiety and social vigilance and reductions of the latter with reduced social affiliation. We sought to test the hypothesis that, within the primate macaque genus, the more gregarious, affiliative, and affectively stable bonnet species (Macaca radiata) would exhibit lower cerebrospinal fluid (CSF) CRF and higher CSF OT concentrations in comparison to its close relative, the temperamentally volatile and socially distant pigtail (Macaca nemestrina). Cisternal CSF samples were obtained from young adult male and female pigtail and bonnet macaques, and CRF and OT concentrations were measured by radioimmunoassay. Pigtail macaques exhibited significantly higher concentrations of CSF CRF and significant lower concentrations of CSF OT than bonnet macaques. Results were not attributable to age or sex differences in group composition. When included together in a multiple regression, CRF and OT showed a multiple R of 0.76, accounting for more than half of the species variance. Although species differences in the bioeffectiveness of these peptides may possibly confound the observed biobehavioral relationships, in the absence of any existing data to that effect, the current findings appear in accordance with the hypothesis and consistent with previously reported species-typical behaviors observed in these macaques.