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Alpha 1-adrenergic constriction limits coronary flow and cardiac function in running dogs
The American Journal of Physiology
|June 1, 1986
Summary
Alpha 1-adrenergic receptors limit cardiac function and coronary vasodilation during strenuous exercise. Blocking these receptors enhanced myocardial oxygen delivery and cardiac performance in dogs.
Area of Science:
- Cardiovascular Physiology
- Adrenergic Receptor Pharmacology
Background:
- Alpha 1-adrenergic receptors play a role in regulating cardiovascular function.
- Understanding their precise role during physiological stress like exercise is crucial.
Purpose of the Study:
- To investigate the role of alpha 1-adrenergic receptors in modulating coronary blood flow and cardiac function during strenuous exercise in dogs.
Main Methods:
- Chronically instrumented dogs were subjected to strenuous exercise.
- Local alpha 1-adrenergic blockade was achieved using prazosin or phentolamine.
- Measurements included coronary blood flow, heart rate, and left ventricular function.
Main Results:
- Exercise increased heart rate, blood pressure, and cardiac function.
- Alpha 1-blockade with prazosin or phentolamine further increased cardiac function (dP/dt, regional shortening) and coronary flow.
- Myocardial oxygen consumption increased without changes in oxygen extraction.
Conclusions:
- Alpha 1-vasoconstriction limits myocardial oxygen delivery during exercise.
- These receptors modulate both coronary vasodilation and cardiac performance under strenuous conditions.