TOTAL CORTISOL, FREE CORTISOL, AND GROWTH-HORMONE ASSOCIATED WITH BRIEF SOCIAL SEPARATION EXPERIENCES IN YOUNG MACAQUES

Many behavioral, immunological, and physiological consequences of brie f maternal separation in bonnet (Macaca radiata) and pigtail monkeys ( Macaca nemistrina) have been documented. However, the impact of social separation on plasma cortisol and growth hormone is unknown for these particular species. In the present study, the behavioral and endocrin ological consequences of a 2-week maternal separation in socially hous ed infant bonnet and pigtail monkeys were followed. In seven pairs (se parated and matched control) of bonnet and six pairs of pigtail infant s, plasma was obtained under baseline, separated, and reunion conditio ns twice weekly for the duration of the study. Blood samples were obta ined from both infants of the pair in approximately 10 min. Plasma tot al cortisol, free cortisol, and growth hormone were measured in these samples. Focal animal behavioral observations were made on all subject s twice daily throughout the study period. In both species, total cort isol and free cortisol rose immediately following maternal separation in comparison to the matched nonseparated controls and returned to bas al levels (e.g., that of matched nonseparated controls) following reun ion with the mother. In contrast, plasma growth hormone rose only in t he pigtail infants over a time course that peaked around the time of r eunion. Multiple regression techniques indicated for the first week of separation, in the separated but not control subjects, that mean plas ma free and total cortisol was positively related to distress behavior s (vocalization and postural slouch) observed during this week and neg atively related to social behaviors (play and proximity to others) not ed during the same period. In contrast, plasma growth hormone was rela ted to both species and sex of the subjects but unrelated to behaviora l variables. (C) 1995 by John Wiley & Sons, Inc.