Reduced vagal activity in salt-sensitive subjects during mental challenge.
BACKGROUND
Salt-sensitive normotensive men exhibit an enhanced pressor and heart rate (HR) response to mental stress. Stress-induced HR acceleration may result from sympathetic activation or vagal withdrawal. We studied the importance of vagal withdrawal for the increased stress responsiveness of salt-sensitive subjects.


METHODS
We studied cardiovascular reactivity to mental challenge in 17 salt-sensitive healthy white male students and 56 salt-resistant control subjects who were comparable with respect to age, body mass index, and physical fitness. Salt sensitivity was determined by a 2-week dietary protocol (20 mmol v 240 mmol sodium/day). Mental stress was induced by a computerized information-processing task (manometer test). Electrocardiogram and finger blood pressure (BP; Finapres, Ohmeda, Louisville, CO) were registered continuously to determine HR and interbeat-interval length. Time and frequency domain (spectral power) based measures of respiratory-related heart rate variability (HRV) were calculated to estimate vagal cardiac control; diastolic BP reactivity was assessed to estimate peripheral sympathetic effects.


RESULTS
Stress-induced increase in HR was higher in salt-sensitive than in salt-resistant subjects. Salt-sensitive subjects, in comparison to salt-resistant subjects, showed significantly reduced respiratory-related HRV during baseline and mental stress conditions (P <.01). The increase in diastolic BP during mental challenge was significantly greater in salt-sensitive subjects (P <.05).


CONCLUSIONS
Our findings suggest reduced vagal and increased sympathetic tone during mental challenge in salt-sensitive subjects. Altered autonomic nervous system function may contribute to later development of hypertension in salt-sensitive individuals.
Buchholz
Konrad
K
Division of Psychosomatic Medicine, Benjamin Franklin Medical Center, Free University of Berlin, Berlin, Germany. konrad.bucholz@gmx.de
Schächinger
Hartmut
H
Wagner
Miriam
M
Sharma
Arya M
AM
Deter
Hans Christian
HC
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology / Q000503:physiopathology; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D004562:Electrocardiography; D006801:Humans; D008297:Male; D009424:Nervous System Physiological Phenomena; D012146:Rest / Q000502:physiology; D012492:Salts / Q000378:metabolism*; D013315:Stress, Psychological / Q000378:metabolism* / Q000503:physiopathology; D014630:Vagus Nerve / Q000502:physiology* / Q000503:physiopathology
D012492:Salts