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Journal of Comparative Physiology A

, Volume 176, Issue 5, pp 653–660 | Cite as

Excitatory action of the bird antidiuretic hormone vasotocin on neurons in the subfornical organ

  • H. A. Schmid
  • F. Schäfer
  • E. Simon
Original Paper

Abstract

The responsiveness of spontaneously active neurons in the subfornical organ (SFO) of adult ducks to angiotensin II (ANGII) and the bird specific anti-diuretic hormone, arginine vasotocin (AVT), the analog of the mammalian arginine vasopressin (AVP), were investigated in brain slices with extracellular recording technique. 65% (n = 66) of the neurons increased their activity after superfusion with ANGII, the rest were unresponsive. Application of AVT activated 52% (n = 68) of the investigated neurons and like ANGII never caused an inhibition of the spontaneously active SFO neurons. A close correlation exists between the ANGII and AVT sensitivity of duck SFO neurons, because 29 out of 33 neurons were excited by AVT as well as ANGII. The relatively weak antagonistic effect of the V1-type receptor antagonist Pmp-Tyr (Me)-Arg8-vasopressin on the AVT induced excitation suggests a different pharmacology of the bird AVT receptor as compared to the mammalian AVP receptor. The excitatory response of ANGII and AVT on the very same neurons suggest a similar function of both peptides on SFO mediated effects in vivo, such as an increase in water intake. However, peripheral AVT concentrations, unlike ANGII concentrations in the blood are not high enough to activate SFO neurons from the blood side of the blood brain barrier. Therefore AVT is presumably released from synapses of neurons originating within or projecting to the SFO. The identity of the ANGII and AVT reactive neurons suggests that synaptically released AVT should facilitate SFO mediated drinking.

Key words

Osmoregulation Duck Antidiuretic hormone Vasotocin Subfornical organ Drinking Thrist Vasopressin 

Abbreviations

aCSF

artificial cerebrospinal fluid

ANGII

angiotensin II

AVT

arginine vasotocin

AVP

arginine vasopressin

ADH

antidiuretic hormone

SFO

subfornical organ

AVP4–9

arginine-vasopressin fragment 4–9

BBB

blood-brain barrier

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Copyright information

© Springer-Verlag 1995

Authors and Affiliations

  • H. A. Schmid
    • 1
  • F. Schäfer
    • 1
  • E. Simon
    • 1
  1. 1.Max-Planck-Institut für physiologische und klinische Forschung, W.G. Kerckhoff-InstitutBad NauheimGermany

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