NEUROENDOCRINE RESPONSES TO FENFLURAMINE CHALLENGE ARE INFLUENCED BY EXPOSURE TO CHRONIC SOCIAL STRESS IN ADULT MALE CYNOMOLGUS MACAQUES

This study was designed to investigate the effect of chronic social st ress on central serotonergic responsivity in adult male cynomolgus mon keys (Macaca fascicularis). The influences of social stress and domina nce status (social rank) on adrenocorticotropin hormone (ACTH) and cor tisol responses to acute administration of an indirect serotonergic ag onist (fenfluramine) were evaluated in 75 cynomolgus macaques that wer e housed in five-member social groups for 28 mo. These groups either r emained stable in composition (No-Stress) or had their composition per iodically reorganized in the first (Early-Stress) or second (Late-Stre ss) halves of the study. At the end of the 23rd month, a fenfluramine challenge was done. Animals in the Late-Stress condition had significa ntly higher ACTH responses compared to those in the No-Stress conditio n (p < .05) and significantly higher cortisol responses compared to th ose in the Early-Stress condition (p < .05). No differences between do minant and subordinate animals in ACTH or cortisol responses to challe nge were identified. These data suggest that social stress produces a ''state''-related augmentation of hypothalamic-pituitary-adrenal respo nsivity to fenfluramine (serotonergic) challenge in cynomolgus macaque s.