Differential effects of aging on fluid intake in response to hypovolemia, hypertonicity, and hormonal stimuli in Munich Wistar rats.

Bibliographic Collection: 
CARTA-Inspired Publication
Publication Type: Journal Article
Authors: McKinley, MJ; Denton, DA; Thomas, CJ; Woods, RL; Mathai, ML
Year of Publication: 2006
Journal: Proc Natl Acad Sci U S A
Volume: 103
Number: 9
Pagination: 3450-5
Date Published: Feb 28
Publisher: United States
Publication Language: eng
Accession Number: 16492769
Keywords: Adrenergic beta-Agonists/pharmacology, Aging/*physiology, Animals, Body Weight, Dehydration/physiopathology, Drinking/*drug effects/*physiology, Eating, Germany, Hypovolemia/*physiopathology, Injections, Intraperitoneal, Isoproterenol/*pharmacology, Rats

A significant proportion of aged humans may have impaired thirst and inadequate fluid intake after a period of fluid deprivation. We have studied the water drinking responses, relative to body weight, of Munich Wistar (MW) rats in response to osmotic, hypovolemic, dehydrational, and angiotensin (Ang)-related stimuli as they aged from 3 to 24 months. Young 3-months-old (m.o.) rats had the largest daily fluid intakes and drinking responses to hypertonic and dehydrational stimuli, suggesting that they have accentuated thirst in comparison with older age groups. There were no differences in daily fluid intake from 6-24 m.o.; however, drinking responses to i.p. injection of hypertonic 0.4 mol/liter NaCl gradually declined over this period so that in 24-m.o. rats the response was only half that of 6-m.o. rats. Water intake after 24-h water deprivation also declined gradually over 24 months. Drinking responses to hypovolemia induced by s.c. injection of colloid (polyethylene glycol) were unchanged in 6- to 15-m.o. rats, then declined precipitously in 18- to 24-m.o. rats. Drinking responses to s.c. Ang II or s.c. isoproterenol were not reduced in 24-m.o. rats, nor was the drinking associated with feeding. Therefore, there are specific impairments of water intake in response to hypertonicity and hypovolemia in aged MW rats, but Ang-related drinking is not reduced. Like aged humans, aged MW rats exhibit high plasma atrial natriuretic peptide levels and impaired cardiovascular reflexes that could contribute to the impairment of thirst with age.


Proc Natl Acad Sci U S A. 2006 Feb 28;103(9):3450-5. Epub 2006 Feb 21.

Author Address:

Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Victoria, Australia. mmck@hfi.unimelb.edu.au