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Effects of β-adrenergic receptor agonists on drinking and arterial blood pressure in young and old rats
Journal article   Open access   Peer reviewed

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

Robert L Thunhorst, Connie L Grobe, Terry G Beltz and Alan Kim Johnson
American journal of physiology. Regulatory, integrative and comparative physiology, Vol.300(4), pp.R1001-R1008
04/2011
DOI: 10.1152/ajpregu.00737.2010
PMCID: PMC3075079
PMID: 21307363
url
https://doi.org/10.1152/ajpregu.00737.2010View
Published (Version of record) Open Access

Abstract

These experiments examined water-drinking and arterial blood pressure responses to β-adrenergic receptor activation in young (4 mo), “middle-aged” adult (12 mo), and old (29 mo) male rats of the Brown-Norway strain. We used isoproterenol to simultaneously activate β 1 - and β 2 -adrenergic receptors, salbutamol to selectively activate β 2 -adrenergic receptors, and the combination of isoproterenol and the β 2 -adrenergic receptor antagonist ICI 118,551 to stimulate only β 1 -adrenergic receptors. Animals received one of the drug treatments, and water drinking was measured for 90 min. About 1 wk later, animals received the same drug treatment for measurement of arterial blood pressure responses for 90 min. In some rats, levels of renin and aldosterone secretion in response to isoproterenol or salbutamol were measured in additional tests. Old and middle-aged rats drank significantly less after isoproterenol than did young rats and also had greater reductions in arterial blood pressure. Old and middle-aged rats drank significantly less after salbutamol than did young rats, although reductions in arterial blood pressure were equivalent across the ages. The β 2 -adrenergic antagonist ICI 118,551 abolished drinking after isoproterenol and prevented most of the observed hypotension. Renin secretion after isoproterenol and salbutamol was greater in young rats than in middle-aged rats, and wholly absent in old rats. Aldosterone secretion was reduced in old rats compared with young and middle-aged rats after treatment with isoproterenol, but not after treatment with salbutamol. In conclusion, there are age-related differences in β-adrenergic receptor-mediated drinking that can be explained only in part by age-related differences in renin secretion after β-adrenergic receptor stimulation.
 hematocrit heart rate aging water intake aldosterone renin activity

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