HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (5) Citing Articles via Google Scholar Google Scholar Articles by Ilyinsky, O. Articles by Mifflin, S. Search for Related Content PubMed PubMed Citation Articles by Ilyinsky, O. Articles by Mifflin, S.

CARDIAC, RENAL, AND RESPIRATORY INTEGRATION

Chronic hypoxia abolishes posthypoxia frequency decline in the anesthetized rat

Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900

Submitted 22 January 2003 ; accepted in final form 31 July 2003

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.

chemoreceptor; carotid body; respiration; phrenic nerve discharge, acute hypoxia

This article has been cited by other articles:

				Y.-H. Hsieh, T. E. Dick, and R. E. Siegel Adaptation to hypobaric hypoxia involves GABAA receptors in the pons Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2008; 294(2): R549 - R557. [Abstract] [Full Text] [PDF]

				T. A. Day and R. J. A. Wilson Brainstem PCO2 modulates phrenic responses to specific carotid body hypoxia in an in situ dual perfused rat preparation J. Physiol., February 1, 2007; 578(3): 843 - 857. [Abstract] [Full Text] [PDF]

				T. A. Day and R. J. A. Wilson Specific carotid body chemostimulation is sufficient to elicit phrenic poststimulus frequency decline in a novel in situ dual-perfused rat preparation Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2005; 289(2): R532 - R544. [Abstract] [Full Text] [PDF]

				C. J Madden and S. F Morrison Hypoxic activation of arterial chemoreceptors inhibits sympathetic outflow to brown adipose tissue in rats J. Physiol., July 15, 2005; 566(2): 559 - 573. [Abstract] [Full Text] [PDF]