title: The Content of Thyroid Hormone Receptor α in Ewe Kisspeptin Neurones is not Season-Dependent.
abstract: Seasonal reproduction is grounded in several mechanisms, among which are plasticity in both hormone synthesis and neuronal networks. Increased daylength on long days (LD) translates into local tri-iodothyronin (T3) production in the mediobasal hypothalamus that will enable the transition to the anoestrus season in sheep. The photoperiod also strongly affects the content of kisspeptin (Kiss), a hypothalamic neuropeptide exerting a potent stimulatory effect on gonadotrophin-releasing hormone release. Our hypothesis was that T3 directly inhibits Kiss release during LD. Using double immunocytochemistry, we first searched for coexpression of thyroid hormone receptor (THR)α in Kiss neurones in ewes with an active or inactive gonadotrophic axis. In both the preoptic area and the arcuate nucleus, most Kiss neurones were labelled by THR antibody under both physiological/photoperiodic conditions. These results suggest thyroid hormones may affect Kiss synthesis and release all through the year. We then attempted to assess the influence of T3 on Kiss content in hypothalamic explants sampled from ewes with an active gonadotrophic axis. Kiss produced by hypothalamic explants cultured with different doses of T3 (300 or 600 pg) and subjected to different times of incubation (2 or 24 h) was measured. No significant effects of T3 on Kiss tissular content were observed for the two doses of T3 and for the two incubation times. In light of these findings, potential reasons for the divergent effects of thyroid hormones on Kiss content are discussed. Our data emphasise that the effects of thyroid hormone on Kiss synthesis are not one-sided and may affect a wide range of functions.
authors.affiliation: UMR85 Physiologie de la Reproduction et des Comportements, INRA, F-37380, Nouzilly, France.|UMR 7247, CNRS, Nouzilly, France.|Université de Tours, Tours, France.|IFCE, Nouzilly, France.
authors.forename: L
authors.initials: L
authors.lastname: Dufourny
authors.affiliation: UMR85 Physiologie de la Reproduction et des Comportements, INRA, F-37380, Nouzilly, France.|UMR 7247, CNRS, Nouzilly, France.|Université de Tours, Tours, France.|IFCE, Nouzilly, France.
authors.forename: D
authors.initials: D
authors.lastname: Gennetay
authors.affiliation: UMR85 Physiologie de la Reproduction et des Comportements, INRA, F-37380, Nouzilly, France.|UMR 7247, CNRS, Nouzilly, France.|Université de Tours, Tours, France.|IFCE, Nouzilly, France.
authors.forename: S
authors.initials: S
authors.lastname: Martinet
authors.affiliation: UMR85 Physiologie de la Reproduction et des Comportements, INRA, F-37380, Nouzilly, France.|UMR 7247, CNRS, Nouzilly, France.|Université de Tours, Tours, France.|IFCE, Nouzilly, France.
authors.forename: D
authors.initials: D
authors.lastname: Lomet
authors.affiliation: UMR85 Physiologie de la Reproduction et des Comportements, INRA, F-37380, Nouzilly, France.|UMR 7247, CNRS, Nouzilly, France.|Université de Tours, Tours, France.|IFCE, Nouzilly, France.
authors.forename: A
authors.initials: A
authors.lastname: Caraty
mesh_terms: D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D059648:Kisspeptins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011301:Preoptic Area / Q000378:metabolism; D012621:Seasons; D012756:Sheep; D037021:Thyroid Hormone Receptors alpha / Q000378:metabolism*; D046509:Tissue Culture Techniques; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D059648:Kisspeptins; D037021:Thyroid Hormone Receptors alpha; D014284:Triiodothyronine
keywords: hypothalamic explants; immunocytochemistry; seasonal reproduction; sheep; triiodothyronin