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This Article Full Text Full Text (PDF) All Versions of this Article: 578/3/843    most recent jphysiol.2006.119594v1 Services Email this article to a friend Similar articles in this journal 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 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. Related Collections Respiratory

¹ Department of Physiology and Biophysics, University of Calgary, Alberta, Canada, 3330 Hospital Dr NW, Calgary, Alberta, Canada T2N 4 N1

Inputs from central (brainstem) and peripheral (carotid body) respiratory chemoreceptors are coordinated to protect blood gases against potentially deleterious fluctuations. However, the mathematics of the steady-state interaction between chemoreceptors has been difficult to ascertain. Further, how this interaction affects time-dependent phenomena (in which chemoresponses depend upon previous experience) is largely unknown. To determine how central P_CO2 modulates the response to peripheral chemostimulation in the rat, we utilized an in situ arterially perfused, vagotomized, decerebrate preparation, in which central and peripheral chemoreceptors were perfused separately (i.e. dual perfused preparation (DPP)). We carried out two sets of experiments: in Experiment 1, we alternated steady-state brainstem P_CO2 between 25 and 50 Torr in each preparation, and applied specific carotid body hypoxia (60 Torr P_O2 and 40 Torr P_CO2) under both conditions; in Experiment 2, we applied four 5 min bouts (separated by 5 min) of specific carotid body hypoxia (60 Torr P_O2 and 40 Torr P_CO2) while holding the brainstem at either 30 Torr or 50 Torr P_CO2. We demonstrate that the level of brainstem P_CO2 modulates (a) the magnitude of the phrenic responses to a single step of specific carotid body hypoxia and (b) the magnitude of time-dependent phenomena. We report that the interaction between chemoreceptors is negative (i.e. hypo-additive), whereby a lower brainstem P_CO2 augments phrenic responses resulting from specific carotid body hypoxia. A negative interaction may underlie the pathophysiology of central sleep apnoea in populations that are chronically hypocapnic.

(Received 23 August 2006; accepted after revision 30 October 2006; first published online 2 November 2006)
Corresponding author R. J. A. Wilson: Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1. Email: wilsonr{at}ucalgary.ca

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