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Response of the atrial pacemaker to dobutamine
Acta Physiologica Latino Americana
|January 1, 1977
Summary
Dobutamine acts as a beta-adrenergic agent on rat atrial pacemakers. Its action is direct and not significantly affected by MAO or COMT enzyme inhibition.
Area of Science:
- Pharmacology
- Cardiovascular Physiology
Background:
- Dobutamine is a sympathomimetic amine used clinically.
- Its precise mechanism of action on cardiac pacemakers requires elucidation.
Purpose of the Study:
- To investigate the adrenergic mechanisms underlying dobutamine's action on isolated rat atrial pacemakers.
- To determine if dobutamine is a substrate for monoamine oxidase (MAO) or catechol-O-methyltransferase (COMT).
Main Methods:
- Dose-chronotropic response curves of dobutamine on isolated rat atria were generated.
- Experiments involved reserpinization, cocaine, propranolol, phentolamine, MAO inhibition (pargyline), and COMT inhibition (U-0521).
Main Results:
- Dobutamine exhibited a typical bell-dome dose-chronotropic response curve.
- Cocaine decreased dobutamine sensitivity, while propranolol caused a rightward shift and reduced maximal response.
- Phentolamine did not reveal alpha-adrenergic activity. Enzyme inhibition studies showed no effect on dobutamine's action.
Conclusions:
- Dobutamine functions as a direct-acting beta-adrenergic agent on rat atrial pacemakers.
- It is not a significant substrate for MAO or COMT.
- Its effects are mediated through beta-adrenergic receptors, not alpha-adrenergic receptors.