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Adrenergic control of the cardiovascular system in the turtle Trachemys scripta

Johannes Overgaard^1,*, Jonathan A. W. Stecyk^1,2, Anthony P. Farrell² and Tobias Wang¹

¹ Department of Zoophysiology, Aarhus University, Building 131, 8000 Aarhus C, Denmark
² Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada

View larger version (24K): [in a new window]   Fig. 1. (A) Effects of adrenergic agonists and antagonists on haemodynamic variables in the turtle Trachemys scripta. Recordings from one individual (#15/group 1) of mean arterial blood pressures and mean blood flows in the pulmonary and systemic circuits, as well as heart rate (fH). Ppul and Psys are the arterial pressures in the pulmonary and systemic circulation, respectively. LAo is blood flow in the left aortic arch, and LPA is the blood flow in the left pulmonary artery. The trace depicts resting conditions and measurements following injections of norepinephrine (norepi), phenylephrine (phenyl) and propranolol (prop). (B) Heart rate and (C) pulmonary and systemic resistances in group 1 turtles (N=6) following injection of agonists and antagonists. a indicates a significant difference (P<0.05) compared with resting conditions, and b indicates a significant difference (P<0.05) compared with the variables obtained following propranolol. Phent, phentolamine.

View larger version (21K): [in a new window]   Fig. 2. (A) Effects of adrenergic agonists and antagonists on haemodynamic variables in the turtle Trachemys scripta. Recordings from one individual (#11/group2) of mean arterial blood pressures and mean blood flows in the pulmonary and systemic circuits, as well as heart rate (fH). Ppul and Psys are the arterial pressures in the pulmonary and systemic circulation, respectively. LAo is blood flow in the left aortic arch, and LPA is the blood flow in the left pulmonary artery. The trace depicts resting conditions and measurements following injections of norepinephrine (norepi), phenylephrine (phenyl) and phentolamine (phent). (B) Heart rate and (C) pulmonary and systemic resistances in group2 turtles (N=6) following injection of agonists and antagonists. a indicates a significant difference (P<0.05) compared with resting conditions, and b indicates significant difference (P<0.05) compared with the variables obtained following phentolamine. Prop, propranolol.

View larger version (29K): [in a new window]   Fig. 3. Effect of norepinephrine dose (1 µg kg-1 or 5 µg kg-1) on (A) heart rate (fH), (B) pulmonary (pul) and systemic (sys) blood flow, (C) pulmonary (Ppul) and systemic (Psys) pressure, (D) pulmonary (Rpul) and systemic (Rsys) resistance, (E) total blood flow (tot) and (F) stroke volume (Vstot). a indicates a significant difference (P<0.05) compared with resting conditions, and b indicates a significant difference (P<0.05) compared with the conditions following injection of 1 µg kg-1 norepinephrine. N=8.

View larger version (23K): [in a new window]   Fig. 4. Effect of isoproteronol (1 µg kg-1) on (A) heart rate (fH), (B) pulmonary (pul) and systemic (sys) blood flow, (C) pulmonary (Ppul) and systemic (Psys) pressure, (D) pulmonary (Rpul) and systemic (Rsys) resistance, (E) total blood flow (tot) and (F) stroke volume (VStot). * indicates a significant difference compared with resting conditions. N=4.

View larger version (19K): [in a new window]   Fig. 5. Relationship between the ratio of vascular resistance (Rpul/Rsys) versus the ratio of blood flows (pul/sys) in the pulmonary and systemic circuits. The box insert shows the same data points on a double-log scale fitted to a power function. All data points are from individual measurements following the protocol of groups 1 and 2. For clarity, individual values with pul/sys of >5 and Rpul/Rsys of >4 were not included in the main figure but are included in the double-log plot.