Sympathetic drive is modulated by central chemoreceptor activation.
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+/-84.0AU) 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+/-65.4AU vs. 183.7+/-104.2AU). 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.
Department of Rehabilitation Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, United States.
Chris
C
Pitsikoulis
Matthew N
MN
Bartels
Gregory
G
Gates
Rebecca A
RA
Rebmann
Aimee M
AM
Layton
Ronald E
RE
De Meersman
D000328:Adult; D001049:Apnea / Q000503:physiopathology*; D001703:Biophysics; D001794:Blood Pressure / Q000502:physiology; D002628:Chemoreceptor Cells / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008297:Male; D012119:Respiration; D016037:Single-Blind Method; D013564:Sympathetic Nervous System / Q000502:physiology*; D055815:Young Adult