The influence of poststress social factors on hormonal reactivity in prepubertal male rats

Abstract

Following a variety of stressors, prepubertal animals display significantly longer hormonal stress responses than adults. Although the mechanisms that mediate this pubertal-related difference in stress reactivity are unclear, previous studies have shown that social interactions are differentially affected by stress in animals before and after puberty. Given the influence of social factors on stress reactivity, we hypothesize the protracted stress-induced hormonal response in prepubertal animals may be in part mediated by aspects of their poststress social environment. We explored this hypothesis by measuring plasma ACTH and corticosterone in prepubertal male rats 15, 30, and 45 min after a 30 min session of restraint stress exposed to one of three social conditions: recovering in the presence of a stressed cage mate; recovering in the presence of a nonstressed cage mate; and recovering in the absence of a cage mate. We report here that although prepubertal and adult animals display different hormonal responses following restraint, the presence or absence of stressed cage mates has little impact on the poststress hormonal response in prepubertal males. We do, however, show that social factors can alter HPA reactivity in prepubertal animals, in that significant hormonal responses are evoked in nonstressed animals exposed to a stressed cage mate, an effect not found in adults. Collectively, these data indicate that although the poststress social environment does not play a role in mediating the protracted hormonal response in prepubertal animals, the social context can significantly influence HPA activation in otherwise unstressed animals prior to puberty.