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Sympathetic nerve activity response to acute intermittent hypoxia (AIH) and development of sympathetic long‐term facilitation (LTF)
Author(s) -
Fong Angelina Y,
Hammond Andrew M,
Xing Tao,
Pilowsky Paul M
Publication year - 2013
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.27.1_supplement.1135.7
Subject(s) - respiratory system , medicine , hypoxia (environmental) , microneurography , sympathetic nervous system , intermittent hypoxia , anesthesia , cardiology , baroreflex , blood pressure , heart rate , chemistry , oxygen , obstructive sleep apnea , organic chemistry
Recent studies found that AIH produces LTF of splanchnic sympathetic nerve activity (sSNA), as well as the well‐described respiratory LTF. This study aimed to further characterize sympathetic LTF in urethane‐anesthetized, vagotomised, ventilated male Sprague‐Dawley rats. Hypoxia (10% O 2 , 45s) elicited increase in phrenic burst frequency and amplitude, sympathoexcitation (235.1 ± 3%) with a corresponding pressor effect (+31.4 ± 4mmHg), and a depressor response on return to the hyperoxia (−16.5 ± 4mmHg). Repeated hypoxia (10x, 5 mins apart) produced consistent respiratory stimulation, depressor and sympathoexcitation. Sympathetic‐respiratory coupling is also unchanged between the 10 stimuli. Total SNA power (0–20Hz) increased during the hypoxic stimulation, but the ratio of cardiac and respiratory frequency components was unchanged. The correlation between the sympathoexcitation and the pressor response declined with repeated hypoxia (Stim 1: +31.4 ± 4mmHg, vs Stim 10: +10.0 ± 2mmHg), indicating adaptation of the vasculature or the neuroeffector junction. At 60 mins after AIH, sSNA was elevated by 60±12.7% (n=4) above baseline. The pattern of respiratory‐sympathetic coupling, total power and the frequencies correlating to the cardiac and respiratory components in the sSNA was unchanged. These data support the idea that sympathetic LTF is due to increase in sympathetic tone. Funding: ARC, NHMRC, MQ.