title: Neurohypophysial Hormones Regulate Amphibious Behaviour in the Mudskipper Goby.
abstract: The neurohypophysial hormones, arginine vasotocin and isotocin, regulate both hydromineral balance and social behaviors in fish. In the amphibious mudskipper, Periophthalmus modestus, we previously found arginine-vasotocin-specific regulation of aggressive behavior, including migration of the submissive subordinate into water. This migration also implies the need for adaptation to dehydration. Here, we examined the effects of arginine vasotocin and isotocin administration on the amphibious behavior of individual mudskippers in vivo. The mudskippers remained in the water for an increased period of time after 1-8 h of intracerebroventricular (ICV) injection with 500 pg/g arginine vasotocin or isotocin. The 'frequency of migration' was decreased after ICV injection of arginine vasotocin or isotocin, reflecting a tendency to remain in the water. ICV injections of isotocin receptor antagonist with arginine vasotocin or isotocin inhibited all of these hormonal effects. In animals kept out of water, mRNA expression of brain arginine vasotocin and isotocin precursors increased 3- and 1.5-fold, respectively. Given the relatively wide distribution of arginine vasotocin fibres throughout the mudskipper brain, induction of arginine vasotocin and isotocin under terrestrial conditions may be involved also in the preference for an aquatic habitat as ligands for brain isotocin receptors.
authors.affiliation: Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakamoto
authors.affiliation: Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
authors.forename: Yudai
authors.initials: Y
authors.lastname: Nishiyama
authors.affiliation: Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
authors.forename: Aoi
authors.initials: A
authors.lastname: Ikeda
authors.affiliation: Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
authors.forename: Hideya
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Laboratory of Physiology, Atmosphere and Ocean Research Institute, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8564, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Hyodo
authors.affiliation: Department of Life Science, Faculty of Science and Technology, Kinki University, Higashiosaka, Osaka, 577-8502, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Kagawa
authors.affiliation: Ushimado Marine Institute, Faculty of Science, Okayama University, Ushimado, Setouchi, 701-4303, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sakamoto
mesh_terms: D000222:Adaptation, Physiological; D000663:Amphibians / Q000502:physiology*; D000818:Animals; D001127:Arginine Vasopressin / Q000008:administration & dosage / Q000502:physiology*; D005399:Fishes / Q000502:physiology*; D007276:Injections, Intraventricular; D010121:Oxytocin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000502:physiology
chemical_list: D001127:Arginine Vasopressin; D010121:Oxytocin; C008215:isotocin