SOCIOREGULATORY EFFECTS ON SQUIRREL-MONKEY PITUITARY-ADRENAL ACTIVITY- A LONGITUDINAL ANALYSIS OF CORTISOL AND ACTH

Squirrel monkeys show unusually prolonged elevations in plasma cortiso l when separated from like-sex social companions. To determine whether this hypersecretion of cortisol reflects a deficiency in feedback mec hanisms that normally inhibit the prolonged activation of the pituitar y-adrenal axis, we simultaneously measured plasma cortisol and cortico tropin (ACTH) in 30 juvenile monkeys housed in established groups, ind ividual cages, and newly formed groups. As found in recent longitudina l studies of adults, when juveniles were living without companions, me an cortisol titers were consistently higher than those observed when t he same juveniles were living in like-sex social groups. When cortisol was elevated, however, ACTH titers were significantly and chronically reduced. These results suggest that elevated cortisol does inhibit AC TH synthesis or release, and that hypercortisolism in squirrel monkeys living without companions is not a consequence of chronic elevations in ACTH. Similar peculiarities in pituitary-adrenal activity are evide nt in a number of affective disorders in human beings.