Sympathetic discharge and vascular resistance after bed rest

• Published in: Journal of applied physiology (1985) Vol. 84; no. 2; pp. 612 - 617
• Main Authors: Shoemaker, J. Kevin, Hogeman, Cynthia S, Leuenberger, Urs A, Herr, Michael D, Gray, Kristen, Silber, David H, Sinoway, Lawrence I
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Am Physiological Soc 01.02.1998; American Physiological Society
• Subjects: Adaptation, Physiological - physiology; Adult; Aerospace Medicine; Bed Rest; Biological and medical sciences; Blood Pressure - physiology; Forearm - blood supply; Forearm - physiology; Fundamental and applied biological sciences. Psychology; Head-Down Tilt; Humans; Male; Muscle, Skeletal - innervation; Muscle, Skeletal - physiology; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Regional Blood Flow - physiology; Space life sciences; Sympathetic Nervous System - physiology; Vascular Resistance - physiology; Vertebrates: nervous system and sense organs; Non-Nasa Center; Nasa Discipline Musculoskeletal; Sonography; Doppler ultrasound study; Human; Sympathetic nerve; Resistance; Blood vessel; Discharge pattern; Electrophysiology; Neurography; Circulatory system; Sympathetic nervous system; Bed rest; NASA Discipline Musculoskeletal; Non-NASA Center
• ISSN: 8750-7587; 1522-1601
• DOI: 10.1152/jappl.1998.84.2.612

1  Division of Cardiology, The Pennsylvania State University College of Medicine, Hershey 17033; and 2  Lebanon Veterans Affairs Medical Center, Lebanon, Pennslyvania 17042 Shoemaker, J. Kevin, Cynthia S. Hogeman, Urs A. Leuenberger, Michael D. Herr, Kristen Gray, David H. Silber, and Lawrence I. Sinoway. Sympathetic discharge and vascular resistance after bed rest. J. Appl. Physiol. 84(2): 612-617, 1998. The effect of 6° head-down-tilt bed rest (HDBR) for 14 days on supine sympathetic discharge and cardiovascular hemodynamics at rest was assessed. Mean arterial pressure, heart rate ( n  = 25), muscle sympathetic nerve activity (MSNA; n  = 16) burst frequency, and forearm blood flow ( n  = 14) were measured, and forearm vascular resistance (FVR) was calculated. Stroke distance, our index of stroke volume, was derived from measurements of aortic mean blood velocity (Doppler) and R-R interval ( n  = 7). With these data, an index of total peripheral resistance was determined. Heart rate at rest was greater in the post (71 ± 2 beats/min)- compared with the pre-HDBR test (66 ± 2 beats/min; P  < 0.003), but mean arterial pressure was unchanged. Aortic stroke distance during post-HDBR (15.5 ± 1.1 cm/beat) was reduced from pre-HDBR levels (20.0 ± 1.5 cm/beat) ( P  < 0.03). Also, MSNA burst frequency was reduced in the post (16.7 ± 2.8 beats/min)- compared with the pre (25.2 ± 2.6 beats/min)-HDBR condition ( P  < 0.01). Bed rest did not alter forearm blood flow, FVR, or total peripheral resistance. Thus reductions in MSNA with HDBR were not associated with a decrease in FVR. muscle sympathetic nerve activity; forearm vascular resistance; total peripheral resistance; Doppler ultrasound The Journal of Applied Physiology 84(2):612-617 8750-7587/98 $5.00 Copyright © 1998 the American Physiological Society