title: Rapid modulation of hypothalamic Kiss1 levels by the suckling stimulus in the lactating rat.
abstract: In mammals, lactation suppresses GnRH/LH secretion resulting in transient infertility. In rats, GnRH/LH secretion is rescued within 18-48 h after pup separation (PS) and rapidly re-suppressed by subsequent re-exposure of pups. To elucidate the mechanisms underlying these rapid modulations, changes in the expression of kisspeptin, a stimulator of GnRH secretion, in several lactating conditions (normal-lactating; 4-h PS; 18-h PS; 4-h PS +1-h re-exposure of pups; non-lactating) were examined using in situ hybridization. PS for 4 h or 18 h increased Kiss1 expressing neurons in both the anteroventral periventricular nucleus (AVPV) and the arcuate nucleus (ARC), and subsequent exposure of pups re-suppressed Kiss1 in the AVPV. A change in Kiss1 expression was observed prior to the reported time of the change in GnRH/LH, indicating that the change in GnRH/LH results from changes in kisspeptin. We further examined the mechanisms underlying the rapid modulation of Kiss1. We first investigated the possible involvement of ascending sensory input during the suckling stimulus. Injection of the anterograde tracer to the subparafascicular parvocellular nucleus (SPFpc) in the midbrain, which relays the suckling stimulus, revealed direct neuronal connections between the SPFpc and kisspeptin neurons in both the AVPV and ARC. We also examined the possible involvement of prolactin (PRL). Administration of PRL for 1 h suppressed Kiss1 expression in the AVPV but not in the ARC. These results indicate that suckling stimulus rapidly modulates Kiss1 expression directly via neuronal connections and indirectly through serum PRL, resulting in modulation in GnRH/LH secretion.
authors.affiliation: Department of Anatomy and NeurobiologyGraduate School of Medicine, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113-8602, Japan.
authors.forename: Shimpei
authors.initials: S
authors.lastname: Higo
authors.affiliation: Department of Anatomy and NeurobiologyGraduate School of Medicine, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113-8602, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Aikawa
authors.affiliation: Department of Anatomy and NeurobiologyGraduate School of Medicine, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113-8602, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Iijima
authors.affiliation: Department of Anatomy and NeurobiologyGraduate School of Medicine, Nippon Medical School, Sendagi 1-1-5, Bunkyo-ku, Tokyo 113-8602, Japan hozawa@nms.ac.jp.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ozawa
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D059648:Kisspeptins / Q000378:metabolism*; D007774:Lactation / Q000187:drug effects / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000097:blood / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: C491406:Kiss1 protein, rat; D059648:Kisspeptins; D007987:Gonadotropin-Releasing Hormone; D011388:Prolactin; D007986:Luteinizing Hormone
keywords: PRL; gonadotrophin releasing hormone; lactation; reproduction