Document Detail

Chronic hypoxia abolishes posthypoxia frequency decline in the anesthetized rat.
MedLine Citation:
PMID:  14615401     Owner:  NLM     Status:  MEDLINE    
In anesthetized rats, increases in phrenic nerve amplitude and frequency during brief periods of hypoxia are followed by a reduction in phrenic nerve burst frequency [posthypoxia frequency decline (PHFD)]. We investigated the effects of chronic exposure to hypoxia on PHFD and on peripheral and central O2-sensing mechanisms. In Inactin-anesthetized (100 mg/kg) Sprague-Dawley rats, phrenic nerve discharge and arterial pressure responses to 10 s N2 inhalation were recorded after exposure to hypoxia (10 +/- 0.5% O2) for 6-14 days. Compared with rats maintained at normoxia, PHFD was abolished in chronic hypoxic rats. Because of inhibition of PHFD, the increased phrenic burst frequency and amplitude after N2 inhalation persisted for 1.8-2.8 times longer in chronic hypoxic (70 s) compared with normoxic (25-40 s) rats (P < 0.05). After acute bilateral carotid body denervation, N2 inhalation produced a short depression of phrenic nerve discharge in both chronic hypoxic and normoxic rats. However, the degree and duration of depression of phrenic nerve discharge was smaller in chronic hypoxic compared with normoxic rats (P < 0.05). We conclude that after exposure to chronic hypoxia, a reduction in PHFD contributes to an increased duration of the acute hypoxic ventilatory response in anesthetized rats. Furthermore, after exposure to chronic hypoxia, the central network responsible for respiration is more resistant to the depressant effects of acute hypoxia in anesthetized rats.
Oleg Ilyinsky; Gleb Tolstykh; Steve Mifflin
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American journal of physiology. Regulatory, integrative and comparative physiology     Volume:  285     ISSN:  0363-6119     ISO Abbreviation:  Am. J. Physiol. Regul. Integr. Comp. Physiol.     Publication Date:  2003 Dec 
Date Detail:
Created Date:  2003-11-17     Completed Date:  2004-01-07     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  100901230     Medline TA:  Am J Physiol Regul Integr Comp Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  R1322-30     Citation Subset:  IM    
Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.
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MeSH Terms
Acute Disease
Adaptation, Physiological / physiology*
Anoxia / physiopathology*
Carotid Body / physiology*
Chronic Disease
Nitrogen / pharmacology
Phrenic Nerve / physiology
Rats, Sprague-Dawley
Grant Support
Reg. No./Substance:

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