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Interaction between carotid baroreflex and exercise pressor reflex depends on baroreceptor afferent input
1Departments of Physiology and Internal Medicine, Dallas, Texas, USA. jpotts@mednet.swmed.edu
The American Journal of Physiology
|June 5, 1998
Summary
The level of arterial baroreceptor input significantly influences the exercise pressor reflex. High baroreceptor input attenuates sympathetic excitation during muscle contraction, while low input facilitates it.
Area of Science:
- Cardiovascular Physiology
- Neuroscience
- Exercise Physiology
Background:
- Arterial baroreceptors and skeletal muscle receptors send afferent signals to cardiovascular control centers in the brainstem.
- The interaction between these inputs is crucial for regulating heart rate and blood pressure during physical activity.
Purpose of the Study:
- To investigate how carotid sinus baroreceptor afferent input (CSA) affects reflex heart rate (HR) and mean arterial pressure (MAP) responses to skeletal muscle afferent (SMA) activation.
- To determine if baroreceptor input modulates the exercise pressor reflex.
Main Methods:
- Experiments were conducted on anesthetized, vagotomized dogs.
- Carotid sinus pressure was servo-controlled to manipulate CSA levels (low and high).
- SMA activation was achieved through induced muscle contraction or passive muscle stretch.
Main Results:
- Low CSA levels facilitated increases in HR and MAP during muscle contraction.
- High CSA levels significantly attenuated these reflex responses.
- Passive muscle stretch also evoked sympathoexcitatory responses that were reduced by baroreceptor input.
Conclusions:
- The interaction between the baroreflex and the exercise pressor reflex is dependent on the level of baroreceptor input.
- Arterial baroreceptor input acts as a powerful modulator of sympatho-excitation triggered by skeletal muscle receptors.