Intragastric hypertonic saline increases vasopressin and central
fos immunoreactivity in conscious rats.
Carlson, Scott H., Alvin Beitz, and John W. Osborn.
University of Minnesota, St. Paul, MN 55108, Departments of
Physiology, Veterinary Pathobiology and Animal Science
APStracts 3:0345R, 1996.
While experimental evidence supports peripheral osmoreceptor
modulation of arginine vasopressin (AVP) release, a local osmotic
signal required for osmoreceptor activation has yet to be identified
using physiological sodium loads. Additionally, the central pathway
involved in peripheral control of AVP has not been clearly
established. Experiments were conducted to examine the effect of
intragastric saline on portal venous osmolality, plasma AVP (PAVP),
and fos immunoreactivity. In anesthetized rats, intragastric infusion
(2.9 ml) of hypertonic (600 mOsm/L) saline significantly increased
portal venous osmolality while systemic blood osmolality remained
constant. In conscious rats, intragastric hypertonic saline
significantly elevated PAVP (3.6 1.3 to 5.8 1.9 pg/ml), whereas no
changes were observed in plasma osmolality in either the isotonic
(296.2 1.4 to 297.6 1.1 mOsm/L) or hypertonic (291.7 1.7 to 291.4 1.8
mOsm/L) group. Finally, intragastric hypertonic saline significantly
increased fos immunoreactivity in the nucleus tractus solitarius
(NTS), area postrema (AP), lateral parabrachial nucleus (LPBN),
supraoptic nucleus (SON), and paraventricular nucleus (PVN). These
results indicate that intragastric hypertonic saline produces a
portal venous osmotic signal that triggers peripheral osmoreceptors
to stimulate AVP release while activating the NTS, AP, LPBN in
addition to the SON and PVN.
Received 9 May 1996; accepted in final form 26 August 1996.
APS Manuscript Number R260-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996