Abstract
A method is described for the simultaneous measurement of cardiac output (CO), using the thermodilution method, and arterial blood pressure in conscious unrestrained rats. For the injection of the indicator solution (ice-cold, 0.9% saline) and for the measurement of systolic and diastolic blood pressure, chronicallyimplanted polyethylene catheters were used, while CO was measured transpulmonarily with a commercially available CO computer and an acutely-implanted (via caudal artery) arterial thermistor catheter. The following were observed in 10 rats at rest: a CO of 40.2 ± 1.9 ml min 100 g , a mean arterial blood pressure of 106 ± 5 mmHg, a heart rate of 417 ± 20 beats min and a peripheral vascular resistance of 2.68 ± 0.13 mmHg (ml min 100 g) . After injection of the β-adrenergic agonist isoprenaline, there was a rise in CO and heart rate, while peripheral resistance and blood pressure were lowered. Injection of the β-receptor-blocked propranolol caused decreases in CO and heart rate, while peripheral resistance and blood pressure rose. It is concluded, that the method described here for the simultaneous measurement of CO and arterial blood pressure is suitable for the investigation of drug-induced cardiovascular effects in conscious rats.
Published Version
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