Estradiol (E2) inhibits fluid intake in several species, which may help to defend fluid homeostasis by preventing excessive extracellular fluid volume. Although this phenomenon is well established using the rat model, it has only been studied directly in young adults. Because aging influences the neuronal sensitivity to E2 and the fluid intake effects of E2 are mediated in the brain, we tested the hypothesis that aging influences the fluid intake effects of E2 in female rats. To do so, we examined water and NaCl intake in addition to the pressor effect after central angiotensin II treatment in young (3–4 months), middle-aged (10–12 months), and old (16–18 months) ovariectomized rats treated with estradiol benzoate (EB). As expected, EB treatment reduced water and NaCl intake in young rats. EB treatment, however, did not reduce water intake in old rats, nor did it reduce NaCl intake in middle-aged or old rats. The ability of EB to reduce blood pressure was, in contrast, observed in all three age groups. Next, we also measured the gene expression of estrogen receptors (ERs) and the angiotensin type 1 receptor (AT1R) in the areas of the brain that control fluid balance. ERβ, G protein estrogen receptor (GPER), and AT1R were reduced in the paraventricular nucleus of the hypothalamus in middle-aged and old rats, compared to young rats. These results suggest the estrogenic control of fluid intake is modified by age. Older animals lost the fluid intake effects of E2, which correlated with decreased ER and AT1R expression in the hypothalamus.
|State||Published - Jul 2021|
Bibliographical noteFunding Information:
This work was supported by the National Institutes of Health grant DA035150, NSF grant 2019346, and University of Kentucky, College of Arts and Sciences Start-Up Funds. We thank Julia Howell and Calista Whorf for technical assistance, Aviv Brockman for statistical advice, and Derek Daniels for comments on the manuscript.
This work was supported by the National Institutes of Health grant DA035150, NSF grant 2019346, and University of Kentucky, College of Arts and Sciences Start‐Up Funds.
© 2021 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society
- NaCl intake
- estrogen receptor
- water intake
ASJC Scopus subject areas
- Physiology (medical)