title: Stimulatory effect of RFRP-3 on the gonadotrophic axis in the male Syrian hamster: the exception proves the rule.
abstract: In seasonal mammals, a distinct photoneuroendocrine circuit that involves the pineal hormone melatonin tightly synchronizes reproduction with seasons. In the Syrian hamster, a seasonal model in which sexual activity is inhibited by short days, we have previously shown that the potent GnRH stimulator, kisspeptin, is crucial to convey melatonin's message; however, the precise mechanisms through which melatonin affects kisspeptin remain unclear. Interestingly, rfrp gene expression in the neurons of the dorsomedial hypothalamic nucleus, a brain region in which melatonin receptors are present in the Syrian hamster, is strongly down-regulated by melatonin in short days. Because a large body of evidence now indicates that RFamide-related peptide (RFRP)-3, the product of the rfrp gene, is an inhibitor of gonadotropin secretion in various mammalian species, we sought to investigate its effect on the gonadotrophic axis in the Syrian hamster. We show that acute central injection of RFRP-3 induces c-Fos expression in GnRH neurons and increases LH, FSH, and testosterone secretion. Moreover, chronic central administration of RFRP-3 restores testicular activity and Kiss1 levels in the arcuate nucleus of hamsters despite persisting photoinhibitory conditions. By contrast RFRP-3 does not have a hypophysiotrophic effect. Overall, these findings demonstrate that, in the male Syrian hamster, RFRP-3 exerts a stimulatory effect on the reproductive axis, most likely via hypothalamic targets. This places RFRP-3 in a decisive position between the melatonergic message and Kiss1 seasonal regulation. Additionally, our data suggest for the first time that the function of this peptide depends on the species and the physiological status of the animal model.
authors.affiliation: Institut des Neurosciences Cellulaires et Intégratives, Unité Propre de Recherche Centre National de la Recherche Scientifique 3212, Université de Strasbourg, Département de Neurobiologie des Rythmes, 5 Rue Blaise Pascal, 67084 Strasbourg, France.
authors.forename: Caroline
authors.initials: C
authors.lastname: Ancel
authors.forename: Agnete H
authors.initials: AH
authors.lastname: Bentsen
authors.forename: Marie-Emilie
authors.initials: ME
authors.lastname: Sébert
authors.forename: Manuel
authors.initials: M
authors.lastname: Tena-Sempere
authors.forename: Jens D
authors.initials: JD
authors.lastname: Mikkelsen
authors.forename: Valérie
authors.initials: V
authors.lastname: Simonneaux
mesh_terms: D000818:Animals; D006224:Cricetinae; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D005786:Gene Expression Regulation; D006062:Gonadotropins / Q000378:metabolism*; D059648:Kisspeptins / Q000737:chemistry; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000378:metabolism; D008647:Mesocricetus; D009474:Neurons / Q000378:metabolism; D009479:Neuropeptides / Q000096:biosynthesis* / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D013739:Testosterone / Q000378:metabolism
chemical_list: D006062:Gonadotropins; D059648:Kisspeptins; D009479:Neuropeptides; D010455:Peptides; D016760:Proto-Oncogene Proteins c-fos; C416987:RFamide peptide; D013739:Testosterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D008550:Melatonin