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This Article Full Text Full Text (PDF) All Versions of this Article: 555/3/805    most recent jphysiol.2003.057919v1 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 Google Scholar Google Scholar Articles by Moore, J. P. Articles by Drinkhill, M. J. Search for Related Content PubMed PubMed Citation Articles by Moore, J. P. Articles by Drinkhill, M. J.

Institute for Cardiovascular Research, The School of Medicine, University of Leeds, Leed LS2 9JT, UK

Distension of the main pulmonary artery and its bifurcation are known to result in a reflex vasoconstriction and increased respiratory drive; however, these responses are observed at abnormally high distending pressures. In this study we recorded afferent activity from pulmonary arterial baroreceptors to investigate their stimulus–response characteristics and to determine whether they are influenced by physiological changes in intrathoracic pressure. In chloralose-anaesthetized dogs, a cardiopulmonary bypass was established, the pulmonary trunk and its main branches were vascularly isolated and perfused with venous blood at pulstatile pressures designed to simulate the normal pulmonary arterial pressure waveform. Afferent slips of a cervical vagus were dissected and nerve fibres identified that displayed discharge patterns with characteristics expected from pulmonary arterial baroreceptors. Recordings were obtained with (a) chest open (b) chest closed and resealed, and (c) with phasic negative intrathoracic pressures in the resealed chest. Pressure–discharge characteristics obtained in the open-chest animals indicated that the threshold pulmonary pressure (corresponding to 5% of the overall response) was 17.1 ± 2.9 and the inflexion point of the curve was 29.2 ± 3.3 mmHg (mean ±S.E.M). In closed-chest animals the threshold and inflexion pressures were reduced to 12.0 ± 1.7 and 20.7 ± 1.8 mmHg. Application of phasic negative intrathoracic pressures further reduced the threshold and inflexion pressures to 9.5 ± 1.2 mmHg (P < 0.05 vs. open) and 14.7 ± 0.8 mmHg (P < 0.003 vs. open and P < 0.02 vs. atmospheric). These results indicate that under physiological conditions, with closed-chest and phasic negative intrathoracic pressure changes similar to those associated with normal breathing, activity from pulmonary baroreceptors is obtained at physiological pulmonary arterial pressures in intact animals.

(Received 19 November 2003; accepted after revision 16 January 2004; first published online 23 January 2004)
Corresponding author M. J. Drinkhill: Institute for Cardiovascular Research, The School of Medicine, University of Leeds, Leeds LS2 9JT, UK. Email: cvsmjd{at}leeds.ac.uk