Non-alpha-adrenergic effects on systemic vascular conductance during lower-body negative pressure, static exercise and muscle metaboreflex activation

Aim This study tested the hypothesis that non‐α‐adrenergic mechanisms contribute to systemic vascular conductance (SVC) in a reflex‐specific manner during the sympathoexcitatory manoeuvres. Methods Twelve healthy subjects underwent lower‐body negative pressure (LBNP, −40 mmHg) as well as static hand...

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Veröffentlicht in:	Acta Physiologica Jg. 206; H. 1; S. 51 - 61
Hauptverfasser:	Kiviniemi, A. M., Frances, M. F., Rachinsky, M., Craen, R., Petrella, R. J., Huikuri, H. V., Tulppo, M. P., Shoemaker, J. K.
Format:	Journal Article
Sprache:	Englisch
Veröffentlicht:	Oxford Blackwell Publishing Ltd 01.09.2012 Wiley-Blackwell Wiley Subscription Services, Inc
Schlagworte:	Adrenergic alpha-Antagonists - pharmacology Adrenergic Neurons - physiology Adult arterial pressure regulation Biological and medical sciences Exercise - physiology Female Fundamental and applied biological sciences. Psychology Heart Rate - physiology Humans Lower Body Negative Pressure Male Muscle, Skeletal - drug effects Muscle, Skeletal - physiology phentolamine Phentolamine - pharmacology sympathetic activity Sympathetic Nervous System - physiology Vasoconstriction - physiology Vertebrates: anatomy and physiology, studies on body, several organs or systems Physical exercise arterial pressure regulation α1-Adrenergic receptor sympathetic activity Activation Negative pressure Striated muscle Sympathetic nervous system Vertebrata Alpha blocking agent Mammalia Metaboreflex Autonomic nervous system Arterial pressure Antagonist Hemodynamics Phentolamine
ISSN:	1748-1708, 1748-1716, 1748-1716
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Zusammenfassung:	Aim This study tested the hypothesis that non‐α‐adrenergic mechanisms contribute to systemic vascular conductance (SVC) in a reflex‐specific manner during the sympathoexcitatory manoeuvres. Methods Twelve healthy subjects underwent lower‐body negative pressure (LBNP, −40 mmHg) as well as static handgrip exercise (HG, 20% of maximal force) followed by post‐exercise forearm circulatory occlusion (PECO, 5 min each) with and without α‐adrenergic blockade induced by phentolamine (PHE). Aortic blood flow, finger blood pressure and superficial femoral artery blood flow were measured to calculate cardiac output, SVC and leg vascular conductance (LVC) during the last minute of each intervention. Results Mean arterial pressure (MAP) decreased more during LBNP with PHE compared with saline (−7 ± 7 vs. −2 ± 5%, P = 0.016). PHE did not alter the MAP response to HG (+20 ± 12 and +24 ± 16%, respectively, for PHE and saline) but decreased the change in MAP during PECO (+12 ± 7 vs. +21 ± 14%, P = 0.005). The decrease in SVC and LVC with LBNP did not differ between saline and PHE trials (−13 ± 10 vs. −17 ± 10%, respectively, for SVC, P = 0.379). In contrast, the SVC response to HG increased from −9 ± 12 with saline to + 5 ± 15% with PHE (P = 0.002) and from −16 ± 15 with saline to +1 ± 16% with PHE during PECO (P = 0.003). LVC responses to HG or PECO were not different from saline with PHE. Conclusions Non‐α‐adrenergic vasoconstriction was present during LBNP. The systemic vasoconstriction during static exercise and isolated muscle metaboreflex activation, in the absence of leg vasoconstriction, was explained by an α‐adrenergic mechanism. Therefore, non‐α‐adrenergic vasoconstriction is more emphasized during baroreflex, but not metaboreflex‐mediated sympathetic activation.
Bibliographie:	ark:/67375/WNG-8MLVZLLW-M Finnish Technology Development Centre istex:61A1A21661A4B4BB1A349893DC86518CAB7B524A Paavo Nurmi Foundation Finnish Foundation of Cardiovascular Research Canadian Institutes of Health Research Research Council for Health of the Academy of Finland ArticleID:APHA2447 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 14 content type line 23
ISSN:	1748-1708 1748-1716 1748-1716
DOI:	10.1111/j.1748-1716.2012.02447.x