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Absence of reflex vascular responses from the intrapulmonary circulation in anaesthetised dogs

McMahon, N.C., Drinkhill, M.J., Myers, D.S. and Hainsworth, R. (2000) Absence of reflex vascular responses from the intrapulmonary circulation in anaesthetised dogs. Experimental Physiology, 85 (4). pp. 421-430. ISSN 0958-0670

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The aim of this investigation was to determine whether reflex cardiovascular responses were obtained to localised distension of the intrapulmonary arterial and venous circulations in a preparation in which the stimuli to other major reflexogenic areas were controlled and the lung was shown to possess reflex activity. Dogs were anaesthetised with [alpha]-chloralose, artificially ventilated, the chests widely opened and a cardiopulmonary bypass established. The intrapulmonary region of the left lung was isolated and perfused through the left pulmonary artery and drained through cannulae in the left pulmonary veins via a Starling resistance. Intrapulmonary arterial and venous pressures were controlled by the rate of inflow of blood and the pressure applied to the Starling resistance. Pressures to the carotid, aortic and coronary baroreceptors and heart chambers were controlled. Responses of vascular resistance were assessed from changes in perfusion pressures to a vascularly isolated hind limb and to the remainder of the subdiaphragmatic circulation (flows constant).

The reactivity of the preparation was demonstrated by observing decreases in vascular resistance to large step changes in carotid sinus pressure (systemic vascular resistance decreased by -40 ± 5 %), chemical stimulation of lung receptors by injection into the pulmonary circulation of veratridine or capsaicin (resistance decreased by -32 ± 4 %) and, in the four dogs tested, increasing pulmonary stroke volume to 450 ml (resistance decreased by -24 ± 6 %). However, despite this evidence that the lung was innervated, increases in intrapulmonary arterial pressure from 14 ± 1 to 43 ± 3 mmHg or in intrapulmonary venous pressure from 5 ± 2 to 34 ± 2 mmHg or both did not result in any consistent changes in systemic or limb vascular resistances. In two animals tested, however, there were marked decreases in efferent phrenic nerve activity. These results indicate that increases in pressure confined to the intrapulmonary arterial and venous circulations do not cause consistent reflex vascular responses, even though the preparation was shown to be reflexly active and the lung was shown to be innervated.

Item Type: Article
Copyright, Publisher and Additional Information: © Cambridge University Press
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Medicine and Health (Leeds) > School of Medicine (Leeds) > Leeds Institute of Genetics, Health and Therapeutics (LIGHT) > Academic Unit of Cardiovascular Medicine (Leeds)
Depositing User: Repository Assistant
Date Deposited: 25 May 2006
Last Modified: 10 Jun 2014 10:45
Published Version: http://dx.doi.org/10.1017/S0958067000019461
Status: Published
Publisher: Cambridge University Press
Refereed: Yes
Identification Number: 10.1017/S0958067000019461
URI: http://eprints.whiterose.ac.uk/id/eprint/1234

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