Sympathetic drive is modulated by central chemoreceptor activation

• Published in: Respiratory physiology & neurobiology Vol. 164; no. 3; pp. 373 - 379
• Main Authors: Pitsikoulis, Chris, Bartels, Matthew N, Gates, Gregory, Rebmann, Rebecca A, Layton, Aimee M, De Meersman, Ronald E
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 31-12-2008; Elsevier
• Subjects: Adult; Apnea - physiopathology; Biological and medical sciences; Biophysics; Blood Pressure - physiology; Chemoreceptor; Chemoreceptor Cells - physiology; Electric Stimulation - methods; Female; Fundamental and applied biological sciences. Psychology; Heart Rate - physiology; Humans; Hyperventilation - physiopathology; Male; Medical Education; Muscle sympathetic nerve activity; Pulmonary/Respiratory; Respiration; Single-Blind Method; Sympathetic Nervous System - physiology; Systolic blood pressure; Ventilation; Vertebrates: respiratory system; Young Adult; Muscle sympathetic nerve activity; Systolic blood pressure; Ventilation; Chemoreceptor; Sympathetic nerve; Activation; Striated muscle; Sympathetic nervous system; Respiratory system; Vertebrata; Mammalia; Autonomic nervous system; Blood pressure; Hemodynamics; Pulmonary ventilation; Respiration
• ISSN: 1569-9048; 1878-1519
• DOI: 10.1016/j.resp.2008.08.010

Abstract To determine the effects of central chemoreceptor stimulation upon sympathetic modulation while minimizing baroreceptor influences, we performed a single-blind, counter-balanced, placebo-controlled trial of a modified hypercapnic/hyperoxic rebreathe protocol stimulus to activate the central chemoreflex. Muscle sympathetic nerve activity (MSNA), heart rate, blood pressure, and ventilation were recorded dynamically as subjects transitioned from a hypocapnia to hypercapnia state. The stages of data recording were defined as hyperventilation (HyV), pre-threshold (PreT) and post-threshold (PostT), with threshold being defined as the point of non-linear deviation in ventilation. The changes in MSNA (−4.2 ± 52.4 arbitrary units (AU) vs. 245.0 ± 84.0 AU) and burst count (−0.1 ± 0.7 bursts/segment vs. 2.5 ± 1.7 bursts/segment) were significantly different between control and rebreathe for the HyV to PreT step. There was also a significant difference for PreT to PostT for total MSNA (3.9 ± 65.4 AU vs. 183.7 ± 104.2 AU). In a hypercapnic/hyperoxic state, the central chemoreceptors modulate sympathetic activity below the chemoreflex threshold independently of the baroreceptors, possibly contributing to basal autonomic/sympathetic tone. Central chemoreceptors also appear to play a significant role in sympathetic modulation after the threshold.