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First published online October 5, 2006
Journal of Experimental Biology 209, 4167-4173 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02459

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Cardiovascular changes under normoxic and hypoxic conditions in the air-breathing teleost Synbranchus marmoratus: importance of the venous system

Marianne Skals^1,2,*, Nini Skovgaard^1,2, Edwin W. Taylor^2,3, Cleo A. C. Leite^2,4, Augusto S. Abe² and Tobias Wang^1,2

¹ Zoophysiology, Department of Biological Sciences, University of Aarhus, 8000 Aarhus, Denmark
² Departamento de Zoologia, Centro de Aquicultura, UNESP, Rio Claro, São Paulo, Brazil
³ School of Biosciences, The University of Birmingham, UK
⁴ Department of Physiological Sciences, Federal University of São Carlos, São Paulo, Brazil

View larger version (10K): [in a new window]   Fig. 1. Traces showing a 30 min recording of the breathing pattern and associated changes in cardiac output () and heart rate (fH) in a 200 g S. marmoratus in normoxic water (PO2>130 mmHg). Grey horizontal bars indicate apnoeas and arrows indicate onset of gill ventilation.

View larger version (6K): [in a new window]   Fig. 2. Traces showing an example of a measurement of mean circulatory filling pressure (MCFP) in a 250 g S. marmoratus ventilating its gills in normoxic water (PO2>130 mmHg). PCV, central venous pressure; PDA, dorsal aortic pressure. The arrow indicates occlusion of blood flow from the heart to measure MCFP. PCV after 15–20 s of occlusion was taken as MCFP (1 cmH2O=0.098 kPa).

View larger version (15K): [in a new window]   Fig. 3. Haemodynamic effects during the transition from apnoea (black bars) to gill ventilation (grey bars) in aerated water (PO2>130 mmHg) in S. marmoratus. , cardiac output; VS, stroke volume; fH, heart rate; PCV, central venous blood pressure; MCFP, mean circulatory filling pressure; PDA, dorsal aortic blood pressure. Values are mean ± s.e.m.; N=5–14. *Significant difference relative to no ventilation (1 cmH2O=0.098 kPa).

View larger version (14K): [in a new window]   Fig. 4. Traces showing a 30 min recording of the breathing pattern and associated changes in cardiac output () and heart rate (fH) in a 200 g S. marmoratus in hypoxic water (PO250 mmHg). Grey horizontal bar indicates an apnoea and arrows indicate air-breaths.

View larger version (23K): [in a new window]   Fig. 5. Traces showing the transition from gill ventilation to air-breathing in a 630 g S. marmoratus in hypoxic water (PO250 mmHg). Arrow indicates the transition. PCV, central venous blood pressure; PDA, dorsal aortic blood pressure; , cardiac output; fH, heart rate (1 cmH2O=0.098 kPa).

View larger version (18K): [in a new window]   Fig. 6. Haemodynamic effects of the transition from gill ventilation (grey bars) to air breathing (white bars) in S. marmoratus in hypoxic water (PO250 mmHg). , cardiac output; VS, stroke volume; fH, heart rate; PCV, central venous blood pressure; MCFP, mean circulatory filling pressure; PDA, dorsal aortic blood pressure. Values are mean ± s.e.m.; N=4–15. *Significant difference relative to gill ventilation (1 cmH2O=0.098 kPa).

View larger version (26K): [in a new window]   Fig. 7. Effects of bolus infusions of adrenaline, phenylephrine, and isoproterenol (2 µg kg–1) on haemodynamic variables in S. marmoratus in aerated water (PO2>130 mmHg). Black bars represent control values and grey bars represent values after infusion of the adrenergic agonists. , cardiac output; VS, stroke volume; fH, heart rate; PCV, central venous blood pressure; MCFP, mean circulatory filling pressure; PDA, dorsal aortic blood pressure. Values are mean ± s.e.m.; N=4–9. *Significant difference relative to control values (1 cmH2O=0.098 kPa).