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Sympathetic neural recruitment during severe chemoreflex stimulation (LB732)
Author(s) -
Badrov Mark,
Usselman Charlotte,
Shoemaker J. Kevin
Publication year - 2014
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.28.1_supplement.lb732
Subject(s) - apnea , hypercapnia , medicine , anesthesia , stimulation , microneurography , cardiology , respiratory system , heart rate , baroreflex , blood pressure
Sympathetic neural recruitment during severe chemoreflex stimulation Mark B. Badrov 1 , Charlotte W. Usselman 1 , J. Kevin Shoemaker 1,2 : 1 School of Kinesiology, 2 Department of Physiology and Pharmacology, Western University, London, Ontario, Canada This study tested the hypothesis that severe chemoreflex stress stimulates the recruitment of sub‐populations of previously silent, larger amplitude sympathetic action potentials. Muscle sympathetic nerve activity was measured via microneurography in 7 healthy males (27 ± 2 yrs, 180 ± 4 cm, 82 ± 13 kg; mean ± SD) at baseline and during a maximal end‐inspiratory apnea, which was preceded by a rebreathing protocol designed to elicit progressive hypoxia and hypercapnia, thereby maximizing the severity of sympathoexcitation evoked during the subsequent apnea (End‐apnea: PO 2 = 58 ± 4 Torr; PCO 2 = 55 ± 5 Torr). Compared to baseline, burst frequency (19 ± 6 to 43 ± 10 bursts/min; P < 0.01), burst incidence (37 ± 12 to 73 ± 11 bursts/100 heartbeats; P < 0.01), and mean normalized burst amplitude (30 ± 6 to 56 ± 6 AU; P < 0.001) were increased during apnea. For sympathetic action potential analyses, action potential frequency (211 ± 205 to 617 ± 354 spikes/min; P < 0.01), action potential incidence (408 ± 400 to 1068 ± 598 spikes/100 heartbeats; P < 0.001), and mean action potential content per burst (10 ± 6 to 15 ± 9 spikes/burst; P < 0.05) were increased during apnea compared to baseline. Furthermore, the total number of distinct amplitude‐based ‘clusters’ of action potentials increased from 15 ± 5 at baseline to 19 ± 8 during apnea ( P < 0.05). This was concomitant with an increase in the number of distinct ‘clusters’ per sympathetic burst (5 ± 2 to 6 ± 3 clusters/burst; P < 0.01) during apnea. In conclusion, a neural recruitment strategy exists whereby previously silent sub‐populations of larger amplitude action potentials are recruited as sympathetic activity is elevated during periods of severe chemoreflex stress. Grant Funding Source : Supported by NSERC and CIHR