Effects of β-adrenergic receptor agonists on drinking and arterial blood pressure in young and old rats

American Journal of Physiology-Regulatory, Integrative and Comp

Beltz²,

Johnson

2013

Self Cite

This work examined the effects of age on salt appetite measured in the form of daily saline (i.e., 0.3 M NaCl) drinking in response to administration of deoxycorticosterone acetate (DOCA; 5 mg/kg body wt) using young (4 mo), "middle-aged" adult (12 mo), and old (30 mo) male Brown Norway rats. Water and sodium intakes, excretions, and balances were determined daily. The salt appetite response was age dependent with "middle-aged" rats ingesting the most saline solution followed in order by young and then old rats. While old rats drank the least saline solution, the amounts of saline ingested still were copious and comprise an unambiguous demonstration of salt appetite in old rats. Middle-aged rats had the highest saline preference ratios of the groups under baseline conditions and throughout testing consistent with an increased avidity for sodium taste. There were age differences in renal handling of water and sodium that were consistent with a renal contribution to the greater saline intakes by middle-aged rats. There was evidence of impaired renal function in old rats, but this did not account for the reduced saline intakes of the oldest rats.

mentioning

confidence: 99%

Effects of aging on mineralocorticoid-induced salt appetite in rats

American Journal of Physiology-Regulatory, Integrative and Comp

Beltz²,

Johnson

2013

Self Cite

“…In a series of studies, we observed deficiencies in both osmotic and renin-dependent thirsts in old BN rats (51,52,55,56,60). Notably, the salt appetite response to sodium depletion is greatly reduced-and sometimes absent-in aged rats (3,40,54), even after multiple episodes of sodium depletions (56).…”

Section: Discussionmentioning

confidence: 96%

“…Like the elderly, aged rats show signs of declining thirst, renal function, and cardiovascular responding. Aged rats do not drink as much water as young rats in response to deficits of either intracellular or extracellular water (3,40,51,52,55,56,60). Aged rats have difficulty retaining water and sodium in times of deficit and are slower than young rats to excrete excess water and sodium (1,4,34,40).…”

mentioning

confidence: 99%

“…Aged rats have difficulty retaining water and sodium in times of deficit and are slower than young rats to excrete excess water and sodium (1,4,34,40). Aged rats have greatly reduced baroreflex control of heart rate responses (51,52,55). In addition, aged rats have diminished salt appetite-the seeking and ingesting of salty substances-a companion motivation to thirst.…”

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

American Journal of Physiology-Regulatory, Integrative and Comp

Xue

Beltz

et al. 2015

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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.

“…The elevation of PRA and aldosterone levels observed after isoproterenol treatment (19) were attenuated in Adriamycin-treated rats providing evidence that the renin-angiotensin system is less responsive to blood pressure/volume-related challenges. This result may account for the decreased water intake after isoproterenol treatment and water deprivation and possibly explains the attenuated water and hypertonic saline intakes after Furo/Cap treatment.…”

Section: Discussionmentioning

confidence: 99%

Thirst and sodium appetite in rats with experimental nephrotic syndrome

Johnson

2015

Physiology & Behavior

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Nephrotic syndrome is a renal disease accompanied by abnormal body fluid balance. The present experiments investigated the role of behavioral mechanisms in contributing to disordered fluid homeostasis in rats with experimentally-induced nephrotic syndrome. The studies examined water and sodium ingestion under ad libitum conditions and in response to dehydration-related challenges in rats made nephrotic by treatment with the antibiotic, Adriamycin. Rats with nephrotic syndrome had greater ad libitum water intakes beginning 3 weeks after treatment, but daily sodium (0.3 M NaCl) intakes were not affected. Nephrotic rats showed attenuated water and sodium intakes after combined treatment with furosemide (10 mg/kg) and captopril (2 mg/kg), reduced water intakes after 20 hr of water deprivation, and diminished water intakes, plasma renin activity and aldosterone secretion after subcutaneous isoproterenol (30 μg/kg). However, the Adriamycin-treated animals had normal water intakes in response to subcutaneous hypertonic saline (4% at 0.75 ml/100 g) and central injections of angiotensin II (10, 20, and 50 ng). The results suggest that water and sodium ingestion in response to hypovolemic/hypotensive stimuli are disturbed in nephrotic rats, and provide evidence that the disordered behaviors reflect disturbances of the peripheral renin-angiotensin-aldosterone system.