AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 5 1696-R1703, Copyright © 1997 by American Physiological Society
Long-term effects of AVP-induced neurohumoral interaction via area postrema on body fluid and blood pressure
Y. Nishida, H. Hosomi and V. S. Bishop
Department of Physiology, Kagawa Medical School, Japan.
Arginine vasopressin (AVP) has been known to interact with the central
nervous system via the area postrema (AP), resulting in suppression of
renal sympathetic outflow in short-term studies. We hypothesize that if
this sympathoinhibitory effect lasts long, then the neurohumoral
interaction would enhance urinary output because of the suppression of
neurogenic reuptake of sodium (Na+) and water. Intact (Int) and AP-lesioned
(APX) rabbits were chronically catheterized and housed in metabolic cages.
AVP was intravenously infused (0.1 mU.kg-1.min-1) for 5 consecutive days.
Urine volume and urinary Na+ excretion rates in Int rabbits were lower than
those in APX rabbits during AVP infusion. This smaller urinary output in
Int rabbits was reconfirmed either from the daily balance of water and Na+
or from the body weight, plasma Na+ concentration, and plasma osmolality
data. This result contradicted the hypothesis. Mean arterial pressure was
not altered in either group of rabbits while heart rate was suppressed in
the Int rabbits. These data suggest that AP-mediated long-term action of
AVP augments water retention and sustains bradycardia.
