title: Food restriction negatively affects multiple levels of the reproductive axis in male house finches, Haemorhous mexicanus.
abstract: Nutrition influences reproductive functions across vertebrates, but the effects of food availability on the functioning of the hypothalamic-pituitary-gonadal (HPG) axis in wild birds and the mechanisms mediating these effects remain unclear. We investigated the influence of chronic food restriction on the HPG axis of photostimulated house finches, Haemorhous mexicanus. Food-restricted birds had underdeveloped testes with smaller seminiferous tubules than ad libitum-fed birds. Baseline plasma testosterone increased in response to photostimulation in ad libitum-fed but not in food-restricted birds. Food availability did not, however, affect the plasma testosterone increase resulting from a gonadotropin-releasing hormone-I (GnRH) or a luteinizing hormone (LH) challenge. The number of hypothalamic GnRH immunoreactive (ir) but not proGnRH-ir perikarya was higher in food-restricted than in ad libitum-fed finches, suggesting inhibited secretion of GnRH. Hypothalamic gonadotropin-inhibitory hormone (GnIH)-ir and neuropeptide Y (NPY)-ir were not affected by food availability. Plasma corticosterone (CORT) was also not affected by food availability, indicating that the observed HPG axis inhibition did not result from increased activity of the hypothalamic-pituitary-adrenal (HPA) axis. This study is among the first to examine multilevel functional changes in the HPG axis in response to food restriction in a wild bird. The results indicate that food availability affects both hypothalamic and gonadal function, but further investigations are needed to clarify the mechanisms by which nutritional signals mediate these effects.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA shelley.valle@asu.edu.
authors.forename: Shelley
authors.initials: S
authors.lastname: Valle
authors.affiliation: Universite de Poitiers, Faculté des Sciences Fondamentales et Appliquées, Poitiers F-86022, France.
authors.forename: Elodie
authors.initials: E
authors.lastname: Carpentier
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
authors.forename: Bethany
authors.initials: B
authors.lastname: Vu
authors.affiliation: Department of Biology, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Tsutsui
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA.
authors.forename: Pierre
authors.initials: P
authors.lastname: Deviche
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000097:blood; D046369:Finches / Q000254:growth & development / Q000502:physiology*; D005508:Food Deprivation; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D007028:Hypothalamic Hormones / Q000097:blood; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000502:physiology*; D007986:Luteinizing Hormone / Q000494:pharmacology*; D008297:Male; D017440:Photoperiod; D010913:Pituitary-Adrenal System / Q000502:physiology; D011498:Protein Precursors / Q000494:pharmacology*; D012098:Reproduction / Q000502:physiology; D013737:Testis / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D013739:Testosterone / Q000097:blood*
chemical_list: D007028:Hypothalamic Hormones; D011498:Protein Precursors; C050866:progonadoliberin I; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D007986:Luteinizing Hormone; D003345:Corticosterone
keywords: Gonadal development; Gonadotropin-releasing hormone; Hypothalamic–pituitary–gonadal axis; Luteinizing hormone; Seasonal reproduction; Testosterone