Age- and limb-related differences in the vasoconstrictor response to limb dependency are not mediated by a sympathetic mechanism in humans

Aims We tested the hypotheses that vasoconstrictor responses to limb dependency are: (i) greater in the leg than the arm, (ii) impaired with age and (iii) not sympathetically mediated. Methods Vascular responses to limb dependency (i.e. lowering the limb from heart level to 30 cm below heart level)...

Full description

Saved in:

Bibliographic Details
Published in:	Acta Physiologica Vol. 205; no. 3; pp. 372 - 380
Main Authors:	Snyder, K. A. M., Shamimi-Noori, S., Wilson, T. E., Monahan, K. D.
Format:	Journal Article
Language:	English
Published:	Oxford Blackwell Publishing Ltd 01-07-2012 Wiley-Blackwell Wiley Subscription Services, Inc
Subjects:	adrenergic Adrenergic Antagonists - pharmacology Adult Aged ageing Aging - physiology Arm - blood supply Arm - innervation Biological and medical sciences blood flow Blood Pressure - physiology Brachial Artery - physiology Female Fundamental and applied biological sciences. Psychology Heart Rate - physiology Humans Leg - blood supply Leg - innervation Male Middle Aged myogenic Phentolamine - pharmacology Popliteal Artery - physiology Propranolol - pharmacology Regional Blood Flow - physiology Sympathetic Nervous System - drug effects Sympathetic Nervous System - physiology Vascular Resistance - physiology Vasoconstriction - physiology venoarteriolar Vertebrates: anatomy and physiology, studies on body, several organs or systems Human Senescence Ageing Vasoconstriction Sympathetic nervous system venoarteriolar Blood flow myogenic Vasomotricity Vertebrata Mammalia Autonomic nervous system adrenergic Hemodynamics Age
Online Access:	Get full text
Tags:	Add Tag No Tags, Be the first to tag this record!

Description
Summary:	Aims We tested the hypotheses that vasoconstrictor responses to limb dependency are: (i) greater in the leg than the arm, (ii) impaired with age and (iii) not sympathetically mediated. Methods Vascular responses to limb dependency (i.e. lowering the limb from heart level to 30 cm below heart level) were determined in 17 young and 17 older adults. Indices of blood flow were obtained in the brachial and popliteal arteries (Doppler ultrasound) as well as in the cutaneous circulation (forearm and calf using laser‐Doppler flowmetry). Vasoconstriction was quantified by calculating the indices of vascular resistance as height corrected mean arterial pressure/limb blood velocity or skin flux. A second group of subjects repeated the limb dependency trials after acute systemic sympathetic blockade. Results Limb dependency increased vascular resistance index in the brachial artery (∆59 ± 8%; P < 0.05) and popliteal artery (∆99 ± 10%; P < 0.05 for change in heart level and brachial vs. popliteal) of young and older adults (∆60 + 9% brachial and ∆61 ± 7% popliteal arteries; P < 0.05 for change in heart level and response in popliteal young vs. older adults). In contrast, cutaneous vasoconstrictor responses to limb dependency were similar in the forearm (∆218 ± 29% and ∆200 ± 29% for young and older adults, respectively) and calf (∆257 ± 32% and ∆236 ± 29%; all P < 0.05 from heart level) of young and older adults. Vasoconstrictor responses to limb dependency were not affected by sympathetic blockade in young or older adults. Conclusion These findings indicate that age‐, limb‐, and tissue‐related differences may exist in the vasoconstrictor response to limb dependency in healthy humans, which are not sympathetically mediated.
Bibliography:	istex:C24D2C06B0BA034DE94989B5129AD57FA7EA4410 National Institutes of Health - No. HL92309; No. AG24420; No. M01 RR10732; No. C06 RR016499 ArticleID:APHA2416 ark:/67375/WNG-L64VHRSZ-H ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23
ISSN:	1748-1708 1748-1716
DOI:	10.1111/j.1748-1716.2012.02416.x