AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 6 645-R650, Copyright © 1985 by American Physiological Society
Osmotic thirst and vasopressin release in humans: a double-blind crossover study
P. A. Phillips, B. J. Rolls, J. G. Ledingham, M. L. Forsling and J. J. Morton
Thirst is a subjective sensation. Therefore to investigate further the
nature, intensity, and specificity of osmotic thirst, we studied the
effects of double-blind infusions of hypertonic (0.45 M) and isotonic (0.15
M) saline on subjective ratings and sensations of thirst, water intake,
plasma vasopressin, and body fluids in seven healthy volunteer young men.
Only the hypertonic saline significantly increased plasma sodium
concentration, plasma osmolality, plasma vasopressin concentration, and
visual analog ratings of thirst sensations. Both infusions expanded blood
volume, which was greater with the hypertonic saline infusion. Neither
solution significantly altered mean arterial blood pressure nor plasma
angiotensin levels. Throughout a 60-min drinking period after the
infusions, water intake was always significantly greater after the
hypertonic saline than after the isotonic saline. The subjects described
the thirst sensations as mainly due to a dry unpleasant tasting mouth,
which was promptly relieved by drinking. Visual analog rating changes
confirmed the subjective reports. Finally, the effects on thirst and
vasopressin secretion were observed at plasma sodium concentration and
osmolality changes that are well within the physiological range.
