Biomaterial Database

Influence of resting sympathetic activity on reflex sympathetic responses in normal man. 1995

H P Schobel, and R M Oren, and A L Mark, and D W Ferguson

Department of Internal Medicine, University of Iowa Hospitals and College of Medicine, Iowa City, USA.

Reflex sympathetic responses to physiologic stress are known to be modulated by afferent sensory mechanisms. However, the potential influence of baseline sympathetic tone on these reflex-mediated responses is unclear. To test the hypothesis that the resting level of muscle sympathetic nerve activity (MSNA) influences reflex-mediated changes in MSNA in normal man, MSNA, blood pressure (BP), central venous pressure (CVP), and heart rate (HR) was measured in 38 normal subjects at rest and during deactivation of cardiopulmonary baroreceptors (CPBR) with lower body negative pressure (LBNP; 0 to -15 mmHg). A cold pressor test (CPT) also was performed in 25 subjects. Incremental LBNP decreased CVP (from 5.8 +/- 0.4 to 2.1 +/- 0.4 mmHg) without altering BP or HR, and increased in MSNA burst frequency (from 22.5 +/- 1.4 to 30.2 +/- 1.4 bursts/min). There was no significant correlation between levels of MSNA and any haemodynamic parameter at rest. There was a significant inverse correlation between CPBR sympathetic gain (CPBRSG, slope of the regression line correlating percentage change in MSNA (bursts/min) per mmHg decrease in CVP during non-hypotensive LBNP) and resting MSNA (r = -0.72, p < 0.0001). A significant inverse correlation was also observed between MSNA responses to the CPT (expressed as percentage change in burst frequency from control) and the resting MSNA (r = -0.63, p = 0.008). Sixteen subjects were restudied 3 weeks to 14 months later to determine reproducibility of measurements; resting BP and CVP, HR, and MSNA levels were not different between the two sessions, as was CPBRSG. In ten of these 16 subjects, in whom the CPT was repeated the MSNA response also was not significantly different. These studies demonstrate an inverse relationship between resting MSNA and both cardiopulmonary baroreflex sensitivity and sympathetic neural responses to the non-baroreflex mediated cold pressor stimulus. These findings suggest that resting levels of sympathetic neural activity influence reflex-mediated changes in muscle sympathetic nerve activity.

UI	MeSH Term	Description	Entries
D008150	Lower Body Negative Pressure	External decompression applied to the lower body. It is used to study orthostatic intolerance and the effects of gravitation and acceleration, to produce simulated hemorrhage in physiologic research, to assess cardiovascular function, and to reduce abdominal stress during childbirth.	Abdominal Decompression,Decompression, Abdominal,LBNP
D008297	Male		Males
D009476	Neurons, Efferent	Neurons which send impulses peripherally to activate muscles or secretory cells.	Efferent Neurons,Efferent Neuron,Neuron, Efferent
D011311	Pressoreceptors	Receptors in the vascular system, particularly the aorta and carotid sinus, which are sensitive to stretch of the vessel walls.	Baroreceptors,Receptors, Stretch, Arterial,Receptors, Stretch, Vascular,Stretch Receptors, Arterial,Stretch Receptors, Vascular,Arterial Stretch Receptor,Arterial Stretch Receptors,Baroreceptor,Pressoreceptor,Receptor, Arterial Stretch,Receptor, Vascular Stretch,Receptors, Arterial Stretch,Receptors, Vascular Stretch,Stretch Receptor, Arterial,Stretch Receptor, Vascular,Vascular Stretch Receptor,Vascular Stretch Receptors
D011312	Pressure	A type of stress exerted uniformly in all directions. Its measure is the force exerted per unit area. (McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Pressures
D012018	Reflex	An involuntary movement or exercise of function in a part, excited in response to a stimulus applied to the periphery and transmitted to the brain or spinal cord.
D012129	Respiratory Function Tests	Measurement of the various processes involved in the act of respiration: inspiration, expiration, oxygen and carbon dioxide exchange, lung volume and compliance, etc.	Lung Function Tests,Pulmonary Function Tests,Function Test, Pulmonary,Function Tests, Pulmonary,Pulmonary Function Test,Test, Pulmonary Function,Tests, Pulmonary Function,Function Test, Lung,Function Test, Respiratory,Function Tests, Lung,Function Tests, Respiratory,Lung Function Test,Respiratory Function Test,Test, Lung Function,Test, Respiratory Function,Tests, Lung Function,Tests, Respiratory Function
D001794	Blood Pressure	PRESSURE of the BLOOD on the ARTERIES and other BLOOD VESSELS.	Systolic Pressure,Diastolic Pressure,Pulse Pressure,Pressure, Blood,Pressure, Diastolic,Pressure, Pulse,Pressure, Systolic,Pressures, Systolic
D003080	Cold Temperature	An absence of warmth or heat or a temperature notably below an accustomed norm.	Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D005260	Female		Females