title: Impact of dehydration on the forebrain preoptic recess walls in the mudskipper, Periophthalmus modestus: a possible locus for the center of thirst.
abstract: The forebrain lamina terminalis has not yet been examined for the role of osmosensing in teleosts, although the thirst center is well known to be present in this vascular permeable forebrain region in mammals. Here, we examined vascular permeability and neuronal responsiveness to dehydration in the lamina terminalis of the mudskipper, a euryhaline goby. Evans blue and N-hydroxysulfosuccinimide-biotin both bind to blood proteins, and are impermeable to the blood-brain barrier. Intraperitoneal injection of these probes stained the walls of the preoptic recess (PR) of the third ventricle, indicating increased vascular permeability in this region. When mudskippers kept in isotonic brackish water (ca. 11 psu) were challenged to seawater (ca. 34 psu) for 3 h, body water content showed a 1 % decrease, compared with mudskippers without hypertonic challenge. Simultaneously, the number of immunohistochemically identified cFos-expressing neurons in the anterior parvocellular preoptic nucleus (PPa) of the PR walls increased in a site-specific manner by approximately 1.6-fold compared with controls. Thus, these findings indicate that PPa neurons are activated, following dehydration in mudskippers. Taken together, the vascularly permeable PR walls may be involved in osmosensing, as in the mammalian thirst center.
authors.affiliation: Laboratory of Fish Physiology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Sawako
authors.initials: S
authors.lastname: Hamasaki
authors.affiliation: Department of Anatomy, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, 683-8503, Japan. mtakao@med.tottori-u.ac.jp.
authors.forename: Takao
authors.initials: T
authors.lastname: Mukuda
authors.affiliation: Department of Anatomy, Faculty of Medicine, Tottori University, 86 Nishi-cho, Yonago, 683-8503, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kaidoh
authors.affiliation: Laboratory of Fish Physiology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yoshida
authors.affiliation: Laboratory of Fish Physiology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Uematsu
mesh_terms: D000818:Animals; D003681:Dehydration; D029941:Fish Proteins / Q000378:metabolism; D005399:Fishes / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D010539:Permeability; D016548:Prosencephalon / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012623:Seawater
chemical_list: D029941:Fish Proteins; D016760:Proto-Oncogene Proteins c-fos
keywords: Dehydration; Forebrain; Thirst; Vascular permeability; cFos