HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 104/3/756    most recent 01128.2007v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Strempel, S. Articles by Jordan, J. Search for Related Content PubMed PubMed Citation Articles by Strempel, S. Articles by Jordan, J.

Norepinephrine transporter inhibition alters the hemodynamic response to hypergravitation

¹Franz-Volhard Clinical Research Center, Medical University Charité and Max-Delbrueck-Centrum and HELIOS Klinikum, Berlin; ²German Aerospace Center, Department of Aerospace Medicine, Cologne, Germany; and ³Department of Medicine, Division of Clinical Pharmacology, Autonomic Dysfunction Center, Vanderbilt University School of Medicine, Vanderbilt University, Nashville, Tennessee

Submitted 22 October 2007 ; accepted in final form 4 January 2008

Sympathetically mediated tachycardia and vasoconstriction maintain blood pressure during hypergravitational stress, thereby preventing gravitation-induced loss of consciousness. Norepinephrine transporter (NET) inhibition prevents neurally mediated (pre)syncope during gravitational stress imposed by head-up tilt testing. Thus it seems reasonable that NET inhibition could increase tolerance to hypergravitational stress. We performed a double-blind, randomized, placebo-controlled crossover study in 11 healthy men (26 ± 1 yr, body mass index 24 ± 1 kg/m²), who ingested the selective NET inhibitor reboxetine (4 mg) or matching placebo 25, 13, and 1 h before testing on separate days. We monitored heart rate, blood pressure, and thoracic impedance in three different body positions (supine, seated, standing) and during a graded centrifuge run (incremental steps of 0.5 g for 3 min each, up to a maximal vertical acceleration load of 3 g). NET inhibition increased supine blood pressure and heart rate. With placebo, blood pressure increased in the seated position and was well maintained during standing. However, with NET inhibition, blood pressure decreased in the seated and standing position. During hypergravitation, blood pressure increased in a graded fashion with placebo. With NET inhibition, the increase in blood pressure during hypergravitation was profoundly diminished. Conversely, the tachycardic responses to sitting, standing, and hypergravitation all were greatly increased with NET inhibition. In contrast to our expectation, short-term NET inhibition did not improve tolerance to hypergravitation. Redistribution of sympathetic activity to the heart or changes in baroreflex responses could explain the excessive tachycardia that we observed.

norepinephrine reuptake transporter; cardiovascular regulation; autonomic nervous system; human

This article has been cited by other articles:

				L. L. Karlsson, Y. Kerckx, L. E. Gustafsson, T. E. Hemmingsson, and D. Linnarsson Microgravity decreases and hypergravity increases exhaled nitric oxide J Appl Physiol, November 1, 2009; 107(5): 1431 - 1437. [Abstract] [Full Text] [PDF]