title: Inhibiting influence of testosterone on stress responsiveness during adolescence.
abstract: The maturation of the hypothalamo-pituitary-adrenal (HPA) axis is a key-component of the changes that occur during adolescence. In guinea pigs, HPA responsiveness during late adolescence depends strongly on the quantity and quality of social interactions: Males that lived in a large mixed-sex colony over the course of adolescence exhibit a lower stress response than males that were kept in pairs (one male/one female). Since colony-housed males have higher testosterone (T) levels than pair-housed males, and inhibiting effects of T on HPA function are well known, we tested the hypothesis that the decrease in stress responsiveness found in colony-housed males is due to their high T concentrations. We manipulated T levels in two experiments: 1) gonadectomy/sham-gonadectomy of colony-housed males (which usually have high T levels), 2) application of T undecanoate/vehicle to pair-housed males (which usually have low T levels). As expected, gonadectomized males showed a significantly increased stress response in comparison with sham-gonadectomized males, and T-injected males had a significantly lower stress response than vehicle-injected males. Both experiments thus confirm an inhibiting effect of T on HPA responsiveness during adolescence, which can mediate the influence of social interactions. The reduction in stress responsiveness is hypothesized to have a biologically adaptive value: A sudden increase in glucocorticoid concentrations can enhance aggressive behavior. Thus, pair-housed males might be adapted to aggressively defend their female ('resource defense strategy'), whereas colony-housed males display little aggressive behavior and are capable of integrating themselves into a colony ('queuing strategy').
authors: Department of Behavioural Biology, University of Münster, Badestraße 13, 48149 Münster, Germany. s.luerzel@gmail.com
authors: Stephanie
authors: S
authors: Lürzel
authors: Sylvia
authors: S
authors: Kaiser
authors: Christine
authors: C
authors: Krüger
authors: Norbert
authors: N
authors: Sachser
mesh_terms: D000374:Aggression / Q000187:drug effects; D000818:Animals; D005260:Female; D006168:Guinea Pigs; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D009919:Orchiectomy; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D013315:Stress, Psychological / Q000188:drug therapy*; D013739:Testosterone / Q000008:administration & dosage / Q000097:blood / Q000502:physiology*
chemical_list: D013739:Testosterone; D006854:Hydrocortisone