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Published on: April 13, 2015
Changes in diastolic coronary resistance during submaximal exercise in conditioned dogs
Summary
Partial training in dogs reduces diastolic coronary resistance (DCR) during exercise by altering sympathetic neural activity, not metabolism. This improved coronary blood flow regulation enhances cardiovascular function.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
- Autonomic Nervous System Control
Background:
- Diastolic coronary resistance (DCR) is a key determinant of myocardial oxygen supply.
- Exercise training is known to alter cardiovascular regulation, but the specific impact on coronary vascular control remains under investigation.
- Understanding neurogenic control of coronary vasculature is crucial for optimizing cardiac function during physical activity.
Purpose of the Study:
- To investigate the effects of partial training on diastolic coronary resistance (DCR) in conscious dogs during submaximal exercise.
- To determine the role of adrenergic mechanisms in mediating changes in DCR with partial training.
- To assess whether altered myocardial oxygen consumption contributes to changes in DCR after partial training.
Main Methods:
- Measurements of left circumflex coronary flow, aortic pressure, and heart rate in 10 conscious dogs.
- Calculation of diastolic coronary resistance (DCR) under untrained (UT) and partially trained (PT) conditions.
- Pharmacological blockade of alpha- and beta-adrenergic receptors using phentolamine and propranolol, respectively.
Main Results:
- Submaximal exercise significantly decreased DCR in both UT and PT conditions, with a greater reduction observed in the PT state.
- Alpha-adrenergic blockade did not significantly alter DCR in either condition.
- Beta-adrenergic blockade resulted in higher DCR in UT dogs compared to PT dogs, suggesting a role for beta-adrenergic pathways.
- Myocardial oxygen consumption was not significantly different between UT and PT conditions.
Conclusions:
- Partial training enhances the regulation of coronary blood flow during submaximal exercise.
- The observed changes in DCR with partial training are primarily mediated by altered neurogenic control, specifically a reduction in sympathetic activity on coronary resistance vessels.
- Metabolic adaptations do not appear to significantly contribute to the improved coronary vascular regulation seen with partial training.
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