Meeting Abstract
125.4 Tuesday, Jan. 7 14:45 Programming of the HPA and HPG Axes by Developmental Stress in Song Sparrows SCHMIDT, KL*; MACDOUGALL-SHACKLETON, EA; SOMA, KK; MACDOUGALL-SHACKLETON, SA; Univ. of Western Ontario, London; Univ. of Western Ontario, London; Univ. of British Columbia, Vancouver; Univ. of Western Ontario, London kschmi5@uwo.ca
The hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes exhibit a large degree of developmental plasticity and can be permanently affected by early-life stressors. Although these effects have been well documented in mammals, less is known about how early-life stress affects regulation of these endocrine systems in non-mammalian species. We determined the long-term effects of early-life food restriction or corticosterone (CORT) treatment on the HPA axis of song sparrows (Melospiza melodia), including responses to restraint stress, dexamethasone challenge, and ACTH challenge. In addition, we assessed long-term effects on the HPG axis by measuring sex steroid levels (testosterone in males and 17β-estradiol in females) before and after a gonadotropin-releasing hormone (GnRH) challenge. Both males and females treated with CORT during development had larger increases in CORT in response to ACTH challenge than food-restricted or control birds. Neither treatment affected the responses of CORT to restraint or dexamethasone. CORT-treated males also had higher initial testosterone levels, but neither treatment affected testosterone levels post-GnRH. Lastly, although GnRH challenge failed to increase circulating estradiol levels in females, females exposed to food restriction or CORT treatment had lower estradiol levels than control females. Therefore, exposure to early-life stress had opposite effects on gonadal sex steroid production in male and female song sparrows. These results show that exposure to stress can developmentally program the endocrine system of songbirds and illustrate the importance of considering developmental conditions when determining the factors responsible for inter-individual variation in endocrine regulation.
