title: Dopamine inhibits reproduction in female zebrafish (Danio rerio) via three pituitary D2 receptor subtypes.
abstract: In many teleosts, the stimulatory control of gonadotrope axis by GnRH is opposed by an inhibitory control by dopamine (DA). The functional importance of this inhibitory pathway differs widely from one teleostean species to another. The zebrafish (Danio rerio) is a teleost fish that has become increasingly popular as an experimental vertebrate model. However, the role of DA in the neuroendocrine control of its reproduction has never been studied. Here the authors evaluated in sexually regressed female zebrafish the effects of in vivo treatments with a DA D2 receptor (D2-R) antagonist domperidone, or a GnRH agonist, alone and in combination, on the pituitary level of FSHβ and LHβ transcripts, the gonadosomatic index, and the ovarian histology. Only the double treatment with GnRH agonist and domperidone could induce an increase in the expression of LHβ, in the gonadosomatic index, and a stimulation of ovarian vitellogenesis, indicating that removal of dopaminergic inhibition is required for the stimulatory action of GnRH and reactivation of ovarian function to occur. Using double immunofluorescent staining on pituitary, the authors showed in this species the innervation of LH cells by tyrosine-hydroxylase immunoreactive fibers. Finally, using in situ hybridization and immunofluorescence, the authors showed that the three subtypes of zebrafish DA D2-R (D2a, D2b, and D2c) were expressed in LH-producing cells, suggesting that they all may be involved in mediating this inhibition. These results show for the first time that, in zebrafish, DA has a direct and potent inhibitory action capable of opposing the stimulatory effect of GnRH in the neuroendocrine control of reproduction.
authors.affiliation: Centre National de la Recherche Scientifique, Unité Propre de Recherche 3294, Neurobiologie et Développement, Avenue de la Terrasse, bat 5E, Gif-sur-Yvette, 91198 Cedex, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Fontaine
authors.forename: Pierre
authors.initials: P
authors.lastname: Affaticati
authors.forename: Kei
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Cécile
authors.initials: C
authors.lastname: Jolly
authors.forename: Charlotte
authors.initials: C
authors.lastname: Bureau
authors.forename: Sylvie
authors.initials: S
authors.lastname: Baloche
authors.forename: Françoise
authors.initials: F
authors.lastname: Gonnet
authors.forename: Philippe
authors.initials: P
authors.lastname: Vernier
authors.forename: Sylvie
authors.initials: S
authors.lastname: Dufour
authors.forename: Catherine
authors.initials: C
authors.lastname: Pasqualini
mesh_terms: D000818:Animals; D004294:Domperidone / Q000494:pharmacology*; D004298:Dopamine / Q000502:physiology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists; D007986:Luteinizing Hormone / Q000096:biosynthesis; D010053:Ovary / Q000187:drug effects / Q000502:physiology; D017448:Receptors, Dopamine D2 / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D012098:Reproduction / Q000187:drug effects*; D015027:Zebrafish
chemical_list: D018492:Dopamine Antagonists; D017448:Receptors, Dopamine D2; D007987:Gonadotropin-Releasing Hormone; D004294:Domperidone; D007986:Luteinizing Hormone; D004298:Dopamine