title: The Japanese quail: a model for studying reproductive aging of hypothalamic systems.
abstract: During aging, the decline of neuroendocrine, endocrine, and behavioral components of reproduction ultimately leads to reproductive failure. These studies considered both neuroendocrine and behavioral aspects of reproductive aging in Japanese quail, using chronological age and reproductive status to separate animals into experimental groups. In Study I, age-related changes in the gonadotropin releasing hormone (GnRH-I) system were investigated and a sharp decrease was observed in GnRH-I concentration in the median eminence of aging animals of both sexes, whereas preoptic-lateral septal region GnRH-I concentrations declined only in aging males. Immunohistochemistry confirmed these findings since aging females retained, whereas males lost GnRH-I cells. Functional changes were assessed by in vitro incubation of parasaggittal hypothalamic slices collected from young and old inactive males and females. Results showed reduced baseline GnRH-I release and diminished response to norepinephrine (NE). Deteriorating fertility also correlated with decreased male sexual behavior and loss of aromatase immunoreactive (AROM-ir) neurons in the medial, but not lateral preoptic nucleus (POA). Sexual behavior and AROM-ir were restored with exogenous testosterone, which was associated with increased cell size in the medial POA. Comparison of cell size and number of AROM-ir cells showed that aged sexually active males had fewer, larger AROM-ir cells when compared to young males, suggesting neuroplasticity of specific neural systems and a critical role of estradiol in maintaining reproductive function.
authors.affiliation: Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA. maotting@umd.edu
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Ottinger
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Abdelnabi
authors.forename: Qichang
authors.initials: Q
authors.lastname: Li
authors.forename: Kehong
authors.initials: K
authors.lastname: Chen
authors.forename: Nicola
authors.initials: N
authors.lastname: Thompson
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Harada
authors.forename: Carla
authors.initials: C
authors.lastname: Viglietti-Panzica
authors.forename: Gian Carlo
authors.initials: GC
authors.lastname: Panzica
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001141:Aromatase / Q000378:metabolism; D003370:Coturnix; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism*; D008297:Male; D023421:Models, Animal; D018377:Neurotransmitter Agents / Q000378:metabolism; D012098:Reproduction / Q000502:physiology*; D012726:Sexual Behavior, Animal; D013739:Testosterone / Q000378:metabolism
chemical_list: D018377:Neurotransmitter Agents; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D001141:Aromatase