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The cardiovascular effects of adrenaline, dobutamine and milrinone in rabbits using pressure-volume loops and guinea pig isolated atrial tissue

Cardiovascular Therapeutics Unit, Department of Pharmacology and Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Victoria, Australia

Summary

This study evaluated the effects of milrinone, adrenaline and dobutamine with pressure-volume loops and isolated atrial tissue.
Agonist dose-response curves to incremental drug infusions were acquired in 11 anesthetised rabbits using pressure-volume loops and preload recruitable stroke work indicated contractility. Agonist concentration-response curves were completed in eight guinea pig isolated atria, for effects on atrial rate and force.
Adrenaline and dobutamine increased contractility (P = 0.006 and 0.044), whereas milrinone did not (P = 0.895). Only adrenaline increased myocardial stiffness (P < 0.001). Milrinone decreased vascular resistance (P < 0.001) and elicited the greatest fall in mean arterial pressure (P < 0.001) and increased ejection fraction (P < 0.001). Adrenaline decreased heart rate (P < 0.001), whereas dobutamine and milrinone increased it (P = 0.006 and 0.011). Milrinone increased the force of left atrial contraction, but its inotropic effect was weak and significantly less than with dobutamine and adrenaline (P < 0.001).
Adrenaline acted as an inoconstrictor, dobutamine an inodilator and milrinone predominantly a vasodilator.

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