Physiol. Res. 52: 637-645, 2003

Effects of Lower Body Negative Pressure on Cardiac and Vascular Responses to Carotid Baroreflex Stimulation


Autonomic Laboratory, Department of Neurology, University of Erlangen-Nuremberg, Erlangen, Germany

Received June 24, 2002
Accepted February 27, 2003

The aim of this study was to assess carotid baroreflex responses during graded lower body negative pressure (LBNP). In 12 healthy subjects (age 29±4 years) we applied sinusoidal neck suction (0 to –30 mmHg) at 0.1 Hz to examine the sympathetic modulation of the heart and blood vessels and at 0.2 Hz to assess the effect of parasympathetic stimulation on the heart. Responses to neck suction were determined as the change in spectral power of RR-interval and blood pressure from baseline values. Measurements were carried out during progressive applications (0 to –50 mmHg) of LBNP. Responses to 0.1 and 0.2 Hz carotid baroreceptor stimulations during low levels of LBNP (–10 mmHg) were not significantly different from those measured during baseline. At higher levels of LBNP, blood pressure responses to 0.1 Hz neck suction were significantly enhanced, but with no significant change in the RR-interval response. LBNP at all levels had no effect on the RR-interval response to 0.2 Hz neck suction. The unchanged responses of RR-interval and blood pressure to neck suction during low level LBNP at –10 mmHg suggest no effect of cardiopulmonary receptor unloading on the carotid arterial baroreflex, since this LBNP level is considered to stimulate cardiopulmonary but not arterial baroreflexes. Enhanced blood pressure responses to neck suction during higher levels of LBNP are not necessarily the result of a reflex interaction but may serve to protect the circulation from fluctuations in blood pressure while standing.

Key words
Autonomic nervous system • Baroreflex • Blood pressure • Heart rate variability • Spectral analysis

Reprint requests
Dr Clive M Brown PhD, Autonomic Laboratory, Department of Neurology, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany, e-mail:

© 2003 by the Institute of Physiology, Czech Academy of Sciences