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) All Versions of this Article: 289/2/R532    most recent 00812.2004v1 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 (4) Citing Articles via Google Scholar Google Scholar Articles by Day, T. A. Articles by Wilson, R. J. A. Search for Related Content PubMed PubMed Citation Articles by Day, T. A. Articles by Wilson, R. J. A.

ENVIRONMENTAL, EXERCISE AND RESPIRATORY PHYSIOLOGY

Specific carotid body chemostimulation is sufficient to elicit phrenic poststimulus frequency decline in a novel in situ dual-perfused rat preparation

Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada

Submitted 1 December 2004 ; accepted in final form 26 March 2005

Time-dependent ventilatory responses to hypoxic and hypercapnic challenges, such as posthypoxic frequency decline (PHxFD) and posthypercapnic frequency decline (PHcFD), could profoundly affect breathing stability. However, little is known about the mechanisms that mediate these phenomena. To determine the contribution of specific carotid body chemostimuli to PHxFD and PHcFD, we developed a novel in situ arterially perfused, vagotomized, decerebrate rat preparation in which central and peripheral chemoreceptors are perfused separately (i.e., a nonanesthetized in situ dual perfused preparation). We confirmed that 1) the perfusion of central and peripheral chemoreceptor compartments was independent by applying specific carotid body hypoxia and hypercapnia before and after carotid sinus nerve transection, 2) the PCO₂ chemoresponse of the dual perfused preparation was similar to other decerebrate preparations, and 3) the phrenic output was stable enough to allow investigation of time-dependent phenomena. We then applied four 5-min bouts (separated by 5 min) of specific carotid body hypoxia (40 Torr PO₂ and 40 Torr PCO₂) or hypercapnia (100 Torr PO₂ and 60 Torr PCO₂) while holding the brain stem PO₂ and PCO₂ constant. We report the novel finding that specific carotid body chemostimuli were sufficient to elicit several phrenic time-dependent phenomena in the rat. Hypoxic challenges elicited PHxFD that increased with bout, leading to progressive augmentation of the phrenic response. Conversely, hypercapnia elicited short-term depression and PHcFD, neither of which was bout dependent. These results, placed in the context of previous findings, suggest multiple physiological mechanisms are responsible for PHxFD and PHcFD, a redundancy that may illustrate that these phenomena have significant adaptive advantages.

sleep apnea; respiratory chemosensitivity; working heart-brain stem preparation; control of breathing

This article has been cited by other articles:

				C. Julien, A. Bairam, and V. Joseph Chronic intermittent hypoxia reduces ventilatory long-term facilitation and enhances apnea frequency in newborn rats Am J Physiol Regulatory Integrative Comp Physiol, April 1, 2008; 294(4): R1356 - R1366. [Abstract] [Full Text] [PDF]

				A. Tadjalli, J. Duffin, Y. M. Li, H. Hong, and J. Peever Inspiratory activation is not required for episodic hypoxia-induced respiratory long-term facilitation in postnatal rats J. Physiol., December 1, 2007; 585(2): 593 - 606. [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]