In our own and in other species, physiological responses to stress can be regulated in important ways by the social environment. Although much is known about how the presence of key social partners can reduce the secretion of stress hormones in challenging circumstances, almost nothing is known about how the perception of the presence of the companion is transformed into neural signals that ultimately reduce the stress hormone secretion. These questions will be studied in guinea pigs, a species in which the ability of social partners to reduce stress hormone secretion is well documented. This project will use pharmacological procedures, which temporarily inactivate selected brain regions to determine the effect of those specific regions on stress hormone secretion during challenge, as well as on the reduction of stress hormone secretion in the presence of a close social companion. These studies will provide new basic information on the neural pathways through which stress hormone secretion is regulated by the social environment. The results will also inform later studies aimed at managing the negative consequences of stress exposure. The work will integrate research and undergraduate education by involving promising undergraduates interested in careers in the life sciences in every aspect of the studies.