title: Developmental programming of the HPA and HPG axes by early-life stress in male and female song sparrows.
abstract: Variation in early environmental conditions can have long-term effects on physiology and behavior, a process referred to as developmental programming. In particular, exposure to early-life stressors can have long-term effects on regulation of the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes. 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. In the current study, 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 the 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. Subjects treated with CORT during development had larger increases in CORT in response to ACTH challenge than food-restricted or control subjects. 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. 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.
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada. Electronic address: kschmi5@uwo.ca.
authors.forename: Kim L
authors.initials: KL
authors.lastname: Schmidt
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Macdougall-Shackleton
authors.affiliation: Department of Psychology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Kiran K
authors.initials: KK
authors.lastname: Soma
authors.affiliation: Department of Biology, University of Western Ontario, London, Ontario, Canada; Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada; Department of Psychology, University of Western Ontario, London, Ontario, Canada.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Macdougall-Shackleton
mesh_terms: D000728:Androgens / Q000494:pharmacology; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D003345:Corticosterone / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology; D004958:Estradiol / Q000097:blood; D005260:Female; D005508:Food Deprivation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology*; D008297:Male; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology*; D046370:Sparrows / Q000502:physiology*; D013312:Stress, Physiological; D013315:Stress, Psychological; D013739:Testosterone / Q000494:pharmacology
chemical_list: D000728:Androgens; D000893:Anti-Inflammatory Agents; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D004958:Estradiol; D003907:Dexamethasone; D003345:Corticosterone
keywords: Adrenocorticotropic hormone; Dexamethasone; Food restriction; Glucocorticoid; GnRH; Phenotypic plasticity