This Article Free upon publication Full Text Full Text (PDF) All Versions of this Article: 54/1/127    most recent HYPERTENSIONAHA.109.131417v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Google Scholar Articles by Hart, E. C. Articles by Charkoudian, N. PubMed PubMed Citation Articles by Hart, E. C. Articles by Charkoudian, N. Related Collections Autonomic, reflex, and neurohumoral control of circulation

(Hypertension. 2009;54:127.)
© 2009 American Heart Association, Inc.

Original Articles

Age-Related Differences in the Sympathetic-Hemodynamic Balance in Men

Emma C. Hart; Michael J. Joyner; B. Gunnar Wallin; Christopher P. Johnson; Timothy B. Curry; John H. Eisenach; Nisha Charkoudian

From the Departments of Anesthesiology (E.C.H., M.J.J., C.P.J., T.B.C., J.H.E.) and Physiology and Biomedical Engineering (N.C.), Mayo Clinic, Rochester, Minn; and the Institute of Neuroscience and Physiology (B.G.W.), Sahlgren Academy, Gothenburg University, Gothenburg, Sweden.

Correspondence to Emma C. Hart, Department of Anesthesiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905. E-mail hart.emma{at}mayo.edu

As humans age, the tonic level of activity in sympathetic vasoconstrictor nerves increases and may contribute to age-related increases in blood pressure. In previous studies in normotensive young men with varying levels of resting sympathetic nerve activity, we observed a balance among factors contributing to blood pressure regulation, such that higher sympathetic activity was associated with lower cardiac output and lesser vascular responsiveness to -adrenergic agonists, which limited the impact of high sympathetic activity on blood pressure. In the present study, we tested the hypothesis that older normotensive men would exhibit a similar balance among these variables (sympathetic nerve activity, cardiac output, and -adrenergic responsiveness) but that this balance would be shifted toward higher sympathetic nerve activity values. We measured muscle sympathetic nerve activity, cardiac output, arterial pressure, and forearm vasoconstrictor responses in 17 older men and compared these with previous data collected in 14 younger men. Muscle sympathetic activity (burst incidence) was positively related to diastolic blood pressure in the older men (r=0.49; P=0.05); this relationship was not observed in young men. In addition, there was no relationship between cardiac output and muscle sympathetic activity (r=0.29; P>0.05) or between muscle sympathetic activity and vasoconstrictor responses in the older men (eg, norepinephrine: r=–0.21; P>0.05). Although our older subjects were normotensive, the relationship between muscle sympathetic nerve activity and diastolic blood pressure and the lack of "balance" among the other variables suggest that these changes with aging may contribute to the risk of sympathetically mediated hypertension in older humans.

Key Words: age • cardiac output • sympathetic vasoconstriction • total peripheral resistance • hypertension