Meeting Abstract
Animals can respond to environmental stressors through activation of the hypothalamic-pituitary-adrenal (HPA) axis and subsequent release of glucocorticoids. In the short-term, release of glucocorticoids can facilitate survival and escape from immediate threats. However, chronic, long-term activation of the HPA axis and glucocorticoids (GCs) can have detrimental impacts on fitness and senescence. Recent studies have suggested that the HPA axis may be closely linked with insulin/insulin-like signaling (IIS) pathway, a highly conserved endocrine pathway responsible for regulating resource allocation and stress resistance. Previous work has suggested GCs may play a role in regulating growth hormone (GH) and insulin-like growth factor-1 levels (IGF-1), relative to nutritional conditions. However, little is known about the impacts of chronic stress on the IIS pathway. To test the effect of chronic stress on the IIS pathway we captured adult male house sparrows (Passer domesticus ), brought them into captivity, and randomly assigned them to one of two treatment groups: control and chronic stress. After a period of acclimation, birds in the chronic stress treatment group were exposed to daily rotating stressors for approximately 7 months. Control birds were housed separately and only disturbed during husbandry tasks once a week. At the end of the experiment, liver and pectoralis tissue samples were collected to measure IGF-1, IGF-1 receptor (IGF-1R), IGF-2, and IGF-2 receptor (IGF-2R) gene expression. Baseline and stress-induced corticosterone were measured at 4 separate time points throughout the experiment. We predicted that birds exposed to chronic stress would have reduced IIS signaling than controls. Results will be discussed within the context of life history theory.
