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Episodic but not continuous hypoxia elicits long‐term facilitation of phrenic motor output in rats
Author(s) -
Baker T. L.,
Mitchell G. S.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00215.x
Subject(s) - phrenic nerve , hypoxia (environmental) , intermittent hypoxia , hyperoxia , anesthesia , facilitation , medicine , chemistry , respiratory system , biology , oxygen , neuroscience , lung , organic chemistry , obstructive sleep apnea
1 Intermittent hypoxia elicits long‐term facilitation (LTF) of phrenic motor output in anaesthetized rats. We tested the hypothesis that an equal cumulative duration of continuous hypoxia would not elicit phrenic LTF. 2 Integrated phrenic nerve activity was recorded in urethane‐anaesthetized, vagotomized, paralysed and ventilated rats exposed to: (1) 3 × 3 min hypoxic episodes (inspired O 2 fraction ( F I,O2 ) = 0.11) separated by 5 min hyperoxia ( F I,O2 = 0.5; n = 6 ), (2) 9 min continuous hypoxia ( n = 6 ), or (3) 20 min continuous hypoxia ( n = 7 ). Isocapnia was maintained throughout the protocol. 3 Consistent with previous studies, phrenic amplitude was significantly elevated for at least 1 h following intermittent hypoxia (78 ± 15% 60 min post‐hypoxia; P < 0.05) with an associated increase in burst frequency (11 ± 2.1 bursts min −1 ; P < 0.05). In contrast, 9 or 20 min continuous hypoxia did not elicit LTF of either phrenic amplitude (4.7 ± 5.1 and 10.1 ± 10.2% 60 min post‐hypoxia, respectively; P > 0.05 ) or frequency (4.6 ± 1.3 and 5.1 ± 2 bursts min −1 60 min post‐hypoxia, respectively; P > 0.05 ). 4 The results indicate that hypoxia‐induced long‐term facilitation of phrenic motor output is sensitive to the pattern of hypoxic exposure in anaesthetized rats.