Effects of hypertonic stimuli and arginine vasotocin (AVT) on water absorption response in Japanese treefrog, Hyla japonica

Sho Maejima, Toshiki Yamada, Takayuki Hamada, Kouhei Matsuda, Minoru Uchiyama

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Anuran amphibians do not drink orally but absorb water osmotically through the highly permeable ventral skin. In this cutaneous water absorption, roles of the putative cerebral osmoreceptors and functions of arginine vasotocin (AVT) were examined in the central nervous system of the Japanese treefrog, Hyla japonica. Intracerebroventricular (ICV) or intralymphatic sac (ILS) administration of various hypertonic solutions (NaCl, mannitol and urea) significantly extended the residence time in water in a dose-dependent manner, suggesting facilitation of water absorption in frogs. ICV injection of AVT also increased significantly the residence time in a dose-dependent manner. The water absorption effect of AVT was significantly inhibited by pretreatment of ICV OPC-21268, a vasopressin V1 receptor antagonist. But pre-ICV injection of OPC-31260, a vasopressin V2 receptor antagonist, did not block the water absorption effect of AVT. Extension of the residence time induced by hyperosmotic NaCl (1000 mOsm) ICV injection was significantly inhibited by pretreatment of ICV OPC-21268. The present results showed that increases of osmotic pressure in plasma and/or cerebrospinal fluid stimulate water absorption response, suggesting that osmoreceptors are certainly present in the central nervous system and AVT may directly stimulate water absorption in the treefrog. It is also suggested that AVT activates cellular mechanisms via V1-like but not V2-like receptors in the central nervous system and facilitates water absorption response in the treefrog.

Original languageEnglish
Pages (from-to)196-202
Number of pages7
JournalGeneral and Comparative Endocrinology
Volume157
Issue number2
DOIs
Publication statusPublished - Jun 2008
Externally publishedYes

Keywords

  • Anurans
  • Arginine vasotocin
  • Central nervous system
  • V-like receptor
  • Water absorption response

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Endocrinology

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