AJP - Regulatory, Integrative and Comparative Physiology, Vol 255, Issue 2 248-R251, Copyright © 1988 by American Physiological Society
Changes in vasopressin and cortisol secretion during operant drinking in dehydrated pigs
R. F. Parrott, S. N. Thornton, B. A. Baldwin and M. L. Forsling
Institute of Animal Physiology and Genetics Research, Agricultural and Food Research Council, Babraham, Cambridge, United Kingdom.
Two studies were carried out to examine endocrine changes during a 60-min
period of operant drinking in 24-h dehydrated pigs. Measurements were made
of water intake, osmolality, hematocrit, and plasma concentrations of
lysine vasopressin (LVP) and cortisol during rehydration (experiment 1) and
of fluid intake, osmolality, and LVP levels during consumption of isotonic
saline (experiment 2). Increases in osmolality and LVP produced by
dehydration in experiment 1 were rapidly reversed during rehydration with
the result that osmolality returned to predeprivation levels after 20 min
and LVP after 30 min, but there was no evidence of a decrease in LVP before
absorption. Plasma cortisol concentrations were unaffected by dehydration
although they declined during the final 40 min of experiment 1. In
experiment 2, osmolality remained elevated during saline drinking, but
plasma concentrations of LVP declined abruptly. The results suggest that
oropharyngeal factors inhibiting vasopressin release, revealed during
saline ingestion, are obscured during normal rehydration as a result of the
rapid rate at which water is absorbed by the gut in this species.
