Document Detail

Intermittent hypoxia induces phrenic long-term facilitation in carotid-denervated rats.
MedLine Citation:
PMID:  12391138     Owner:  NLM     Status:  MEDLINE    
Episodic hypoxia elicits a long-lasting augmentation of phrenic inspiratory activity known as long-term facilitation (LTF). We investigated the respective contributions of carotid chemoafferent neuron activation and hypoxia to the expression of LTF in urethane-anesthetized, vagotomized, paralyzed, and ventilated Sprague-Dawley rats. One hour after three 5-min isocapnic hypoxic episodes [arterial Po(2) (Pa(O(2))) = 40 +/- 5 Torr], integrated phrenic burst amplitude was greater than baseline in both carotid-denervated (n = 8) and sham-operated (n = 7) rats (P < 0.05), indicating LTF. LTF was reduced in carotid-denervated rats relative to sham (P < 0.05). In this and previous studies, rats were ventilated with hyperoxic gas mixtures (inspired oxygen fraction = 0.5) under baseline conditions. To determine whether episodic hyperoxia induces LTF, phrenic activity was recorded under normoxic (Pa(O(2)) = 90-100 Torr) conditions before and after three 5-min episodes of isocapnic hypoxia (Pa(O(2)) = 40 +/- 5 Torr; n = 6) or hyperoxia (Pa(O(2)) > 470 Torr; n = 6). Phrenic burst amplitude was greater than baseline 1 h after episodic hypoxia (P < 0.05), but episodic hyperoxia had no detectable effect. These data suggest that hypoxia per se initiates LTF independently from carotid chemoafferent neuron activation, perhaps through direct central nervous system effects.
Ryan W Bavis; Gordon S Mitchell
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.     Date:  2002-07-12
Journal Detail:
Title:  Journal of applied physiology (Bethesda, Md. : 1985)     Volume:  94     ISSN:  8750-7587     ISO Abbreviation:  J. Appl. Physiol.     Publication Date:  2003 Jan 
Date Detail:
Created Date:  2002-12-17     Completed Date:  2003-06-20     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  8502536     Medline TA:  J Appl Physiol (1985)     Country:  United States    
Other Details:
Languages:  eng     Pagination:  399-409     Citation Subset:  IM    
Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin, Madison, 53706, USA.
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MeSH Terms
Anoxia / physiopathology*
Carotid Body / physiopathology*
Chemoreceptor Cells / physiopathology
Neurons, Afferent / physiology
Phrenic Nerve / physiopathology*
Rats, Sprague-Dawley
Time Factors
Grant Support
Comment In:
J Appl Physiol (1985). 2003 Jan;94(1):390   [PMID:  12486026 ]

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