Stress is a concept that has been extensively investigated, although no one definition has been widely accepted. Individuals vary in what they perceive as a stressor and the physiological consequences of a stressful situation are diverse. SEveral factors influence response to a potentially aversive situation, including the control and predictability of the stimuli, prior experience, and the asocial support available. A lack of social supper has been correlated with increased risk of morbidity and mortality in humans and increased pituitary-adrenocortical activity and decreased immune capacity in animals. Using rhesus monkeys, the proposed investigation will focus on a longitudinal comparison of two social groups: one having an established social support network and one newly formed group absent such a network. This approach will further our understanding of the way in which social factors, such as aggression and competition, may induce stress as well as the way in which positive social behaviors, such as grooming, may modulate an animal's response to aversive situations. By relating behavioral measures of changing social relationships to pituitary- adrenocortical activity, we will quantify the progression of developing relationships in the newly formed group and describe fluctuations associated with reproductive status in the established group Further, we will compare subjects' reproductive parameters and maternal competence across groups and relate the differences to social and hormonal variables. Based on observations recorded, we will construct a behavioral index during the initial stages of the study which we will use to predict pituitary- adrenocortical activity in subsequent stages. Physiological challenges and experimental manipulations will complement the preceding descriptive phase of the study. We will evaluate pituitary and adrenal responsivity and dexamethasone resistance in relation to basal hormone and behavioral data. In addition, subjects will be exposed to a novel area alone and with companions and to infant separation while isolated or in the presence of social companions. Finally, we will remove animals from their social group and place them in a single cage to monitor hormonal behavioral changes over time. This study will provide a quantitative evaluation of the role social relationships play in influencing pituitary-adrenocortical responsivity, maternal competency, and reproductive function using an animal model which will control for factors such as nutrition and drug use which often confound human clinical studies. The studies outlined in this proposal will provide longitudinal reference data, heretofor lacking, on pituitary- adrenocortical activity associated with social context and reproductive state complemented with discrete experimental procedures to elucidate the relationship of social factors and the behavioral and hormonal correlates of stress.
