title: Age-related changes in thirst, salt appetite, and arterial blood pressure in response to aldosterone-dexamethasone combination in rats.
abstract: 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.
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, University of Iowa, Iowa City, Iowa robert-thunhorst@uiowa.edu.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Thunhorst
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, Iowa; François M. Abboud Cardiovascular Center, University of Iowa, Iowa City, Iowa.
authors.forename: Baojian
authors.initials: B
authors.lastname: Xue
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, Iowa;
authors.forename: Terry G
authors.initials: TG
authors.lastname: Beltz
authors.affiliation: Department of Psychology, University of Iowa, Iowa City, Iowa; Department of Health and Human Physiology, University of Iowa, Iowa City, Iowa; and Department of Pharmacology, University of Iowa, Iowa City, Iowa; and François M. Abboud Cardiovascular Center, University of Iowa, Iowa City, Iowa.
authors.forename: Alan Kim
authors.initials: AK
authors.lastname: Johnson
mesh_terms: D000375:Aging / Q000502:physiology*; D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001066:Appetite / Q000187:drug effects* / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D003907:Dexamethasone / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D051381:Rats; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*; D013894:Thirst / Q000187:drug effects* / Q000502:physiology
chemical_list: D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D003907:Dexamethasone
keywords: blood pressure; glucocorticoid; heart rate; mineralocorticoid; sodium ingestion
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