Vagal cardiac function and arterial blood pressure stability

• Published in: American journal of physiology. Heart and circulatory physiology 2001-11, Vol.281 (5), p.H1870-H1880
• Main Authors: Wray, D. Walter, Formes, Kevin J, Weiss, Martin S, O-Yurvati, Albert H, Raven, Peter B, Zhang, Rong, Shi, Xiangrong
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-Agonists - administration & dosage; Adult; Atropine - administration & dosage; Baroreflex - drug effects; Baroreflex - physiology; Blood Pressure - drug effects; Blood Pressure - physiology; Female; Glycopyrrolate - administration & dosage; Heart Rate - drug effects; Heart Rate - physiology; Humans; Lower Body Negative Pressure; Male; Muscarinic Antagonists - administration & dosage; Phenylephrine - administration & dosage; Space life sciences; Vagus Nerve - physiology; Valsalva Maneuver
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.2001.281.5.h1870

1  Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth 76107; and 2  Institute for Exercise and Environmental Medicine, Dallas, Texas 75231 This study was designed to investigate the importance of vagal cardiac modulation in arterial blood pressure (ABP) stability before and after glycopyrrolate or atropine treatment. Changes in R-R interval (RRI) and ABP were assessed in 10 healthy young (age, 22 ± 1.8 yr) volunteers during graded lower body negative pressure (LBNP) before and after muscarinic cholinergic (MC) blockade. Transient hypertension was induced by phenylephrine (1 µg/kg body wt), whereas systemic hypotension was induced by bilateral thigh cuff deflation after a 3-min suprasystolic occlusion. Power spectral densities of systolic [systolic blood pressure (SBP)] and diastolic ABP variability were examined. Both antimuscarinic agents elicited tachycardia similarly without significantly affecting baseline ABP. The increase in SBP after phenylephrine injection (+14 ±   2 mmHg) was significantly augmented with atropine (+26 ± 2 mmHg) or glycopyrrolate (+27 ± 3 mmHg) and associated with a diminished reflex bradycardia. The decrease in SBP after cuff deflation ( 9.2   ± 1.2 mmHg) was significantly greater after atropine ( 15 ± 1   mmHg) or glycopyrrolate ( 14 ± 1 mmHg), with abolished reflex tachycardia. LBNP significantly decreased both SBP and RRI. However, after antimuscarinic agents, the reduction in SBP was greater ( P