Effects of aging on mineralocorticoid-induced salt appetite in rats

Thunhorst, Robert L.; Beltz, Terry G.; Johnson, Alan Kim

doi:10.1152/ajpregu.00349.2013

Cited by 9 publications

(11 citation statements)

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“…Mineralocorticoids stimulate salt appetite by direct effects on mineralocorticoid receptors (MR) in the brain (17,41,42,47). The results of this and the previous study (53) suggest that neural pathways "downstream" from key MR in the brain must retain residual function in aged rats. The present work is the second instance of aged rats reliably responding with salt appetite to an administered mineralocorticoid.…”

Section: Discussionsupporting

confidence: 61%

“…Treatment with ALDO stimulated modest, approximately fourfold, increases in salt intake across the age groups on either an absolute or BW basis. We previously demonstrated mineralocorticoid-induced salt appetite in aged rats using daily subcutaneous injections of very high doses (2 mg/day) of DOCA (53). In that study, middle-aged rats drank the most saline solution in response to DOCA, while old rats drank less than young rats only on a BW basis.…”

Section: Discussionmentioning

confidence: 92%

“…Providing only saline solution to drink during mineralocorticoid treatment greatly exacerbates the rise in ABP due to obligatory ingestion of large volumes of sodium with water (e.g., 6, 36). The progression of hypertension in these "ALDO/salt" or "DOCA/salt" models is well described (e.g., 5, 6, 25, 27, 36, 62-64).Mineralocorticoids are also studied for their ability to stimulate salt appetite (33,42,45,50,53,61,65). In behavioral studies of salt appetite, animals are offered frankly hypertonic (typically, 1.8 -3.0% NaCl) saline solutions in choice with water as the drinking fluids.…”

mentioning

confidence: 99%

“…Mineralocorticoids are also studied for their ability to stimulate salt appetite (33,42,45,50,53,61,65). In behavioral studies of salt appetite, animals are offered frankly hypertonic (typically, 1.8 -3.0% NaCl) saline solutions in choice with water as the drinking fluids.…”

mentioning

confidence: 99%

“…In addition, aged rats have diminished salt appetite-the seeking and ingesting of salty substances-a companion motivation to thirst. The salt appetite response to sodium depletion is profoundly impaired-and sometimes absent-in old rats (3,40,54,56); moreover, the salt appetite that arises in response to excess levels of mineralocorticoid hormones is also significantly attenuated in old rats compared with younger rats (53).…”

mentioning

confidence: 99%

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Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats

Thunhorst

Xue

Beltz

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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This work examined the effects of age on daily water and sodium ingestion and cardiovascular responses to chronic administration of the mineralocorticoid, aldosterone (ALDO) either alone or together with the glucocorticoid, dexamethasone (DEX). Young (4 mo), adult (12 mo), and aged (30 mo) male Brown Norway rats were prepared for continuous telemetry recording of blood pressure (BP) and heart rate (HR). Baseline water and sodium (i.e., 0.3 M NaCl) intake, BP, and HR were established for 10 days. Then ALDO (60 μg/day sc) was infused alone, or together with DEX (2.5 or 20 μg/day sc), for another 10 days. Compared with baseline levels, ALDO stimulated comparable increases in daily saline intake at all ages. ALDO together with the higher dose of DEX (i.e., ALDO/DEX20) increased daily saline intake more than did ALDO, but less so in aged rats. Infusion of ALDO/DEX20 increased mean arterial pressure (MAP), and decreased HR, more than did infusion of ALDO. The changes in MAP in response to both treatments depended on age. For all ages, MAP and saline intake increased simultaneously during ALDO, while MAP always increased before saline intake did during ALDO/DEX20. Contrary to our predictions, MAP did not increase more in old rats in response to either treatment. We speculate that age-related declines in cardiovascular responses to glucocorticoids contributed to the attenuated increases in sodium intake in response to glucocorticoids that were observed in older animals.

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Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 92%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats

Thunhorst

Xue

Beltz

et al. 2015

American Journal of Physiology-Regulatory, Integrative and Comp

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Neuroendocrine Regulation of Hydromineral Homeostasis

Mecawi

Ruginsk

Elias

et al. 2015

Comprehensive Physiology

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Since the crucial evolutionary change from an aqueous to a terrestrial environment, all living organisms address the primordial task of equilibrating the ingestion/production of water and electrolytes (primarily sodium) with their excretion. In mammals, the final route for the excretion of these elements is mainly through the kidneys, which can eliminate concentrated or diluted urine according to the requirements. Despite their primary role in homeostasis, the kidneys are not able to recover water and solutes lost through other systems. Therefore, the selective stimulation or inhibition of motivational and locomotor behavior becomes essential to initiate the search and acquisition of water and/or sodium from the environment. Indeed, imbalances affecting the osmolality and volume of body fluids are dramatic challenges to the maintenance of hydromineral homeostasis. In addition to behavioral changes, which are integrated in the central nervous system, most of the systemic responses recruited to restore hydroelectrolytic balance are accomplished by coordinated actions of the cardiovascular, autonomic and endocrine systems, which determine the appropriate renal responses. The activation of sequential and redundant mechanisms (involving local and systemic factors) produces accurate and self-limited effector responses. From a physiological point of view, understanding the mechanisms underlying water and sodium balance is intriguing and of great interest for the biomedical sciences. Therefore, the present review will address the biophysical, evolutionary and historical perspectives concerning the integrative neuroendocrine control of hydromineral balance, focusing on the major neural and endocrine systems implicated in the control of water and sodium balance.

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Age-related declines in thirst and salt appetite responses in male Fischer 344×Brown Norway rats

Thunhorst

Beltz

Johnson

2014

Physiology & Behavior

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The F344xBN strain is the first generational cross between Fischer 344 (F344) and Brown Norway (BN) rats. The F344xBN strain is widely used in aging studies as it is regarded as a model of “healthy” aging (Sprott, 1991). In the present work, male F344xBN rats aged 4 mo (young, n = 6) and 20 mo (old, n = 9) received a series of experimental challenges to body fluid homeostasis to determine their thirst and salt appetite responses. Corresponding urinary responses were measured in some of the studies. Following sodium depletion, old rats ingested less saline solution (0.3 M NaCl) than young rats on a body weight basis, but both ages drank enough saline solution to completely repair the accrued sodium deficits. Following intracellular dehydration, old rats drank less water than young rats, again on a body weight basis, and were less able than young rats to drink amounts of water proportionate to the osmotic challenge. Compared with young rats, old rats drank less of both water and saline solution after combined food and fluid restriction, and also were refractory to the stimulatory effects of low doses of captopril on water drinking and sodium ingestion. Age differences in urinary water and sodium excretion could not account for the age differences in accumulated water and sodium balances. These results extend observations of diminished behavioral responses of aging animals to the F344xBN rat strain and support the idea that impairments in behavior contribute more to the waning ability of aging animals to respond to body fluid challenges than do declines in kidney function. In addition, the results suggest that behavioral defense of sodium homeostasis is less diminished with age in the F344xBN strain compared to other strains so far studied.

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Effects of aging on mineralocorticoid-induced salt appetite in rats

Cited by 9 publications

References 51 publications

Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats

Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats

Neuroendocrine Regulation of Hydromineral Homeostasis

Age-related declines in thirst and salt appetite responses in male Fischer 344×Brown Norway rats

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