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Muscle metaboreflex activation during dynamic exercise evokes epinephrine release resulting in β2-mediated
Jasdeep Kaur1, Marty D Spranger1, Robert L Hammond1
1Department of Physiology and Cardiovascular Research Institute, Wayne State University School of Medicine, Detroit, Michigan.
American Journal of Physiology. Heart and Circulatory Physiology
|December 26, 2014
Summary
Muscle metaboreflex activation (MMA) during exercise increases blood pressure mainly via cardiac output. This study found MMA also causes epinephrine release, leading to vasodilation in non-exercising muscles via beta-2 receptors.
Area of Science:
- Exercise Physiology
- Cardiovascular Regulation
- Autonomic Nervous System
Background:
- Muscle metaboreflex activation (MMA) increases mean arterial pressure (MAP) during exercise, primarily through cardiac output.
- The contribution of peripheral vasculature to this MAP rise during MMA is not fully understood.
Purpose of the Study:
- To investigate the role of peripheral vasculature in MMA-induced MAP increases.
- To determine if epinephrine release mediates vasodilation in non-exercising vascular beds during MMA.
Main Methods:
- Measurements of non-ischemic vascular conductance (NIVC) and plasma epinephrine levels in dogs.
- Experiments conducted during rest, mild exercise, and MMA.
- Pharmacological blockade of alpha-1 and beta-adrenergic receptors (prazosin and propranolol).
Main Results:
- Epinephrine levels and NIVC significantly increased from exercise to MMA.
- Beta-blockade abolished the MMA-induced increase in NIVC.
- Alpha-1 blockade potentiated the increase in NIVC, while combined blockade abolished it.
Conclusions:
- MMA during mild dynamic exercise triggers epinephrine release.
- This epinephrine induces vasodilation in non-exercising vascular beds via beta-2 adrenergic receptors.
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