Dynamic exercise attenuates spontaneous baroreceptor reflex sensitivity in conscious rats

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Exercise Physiology

Background:

• Dynamic exercise is known to attenuate spontaneous baroreceptor reflex sensitivity (sBRS) in humans.
• Endothelial nitric oxide synthase (eNOS) activity within the nucleus tractus solitarii (NTS) has been previously shown to depress sBRS.

Purpose of the Study:

• To investigate the role of eNOS activity within the NTS in the down-modulation of sBRS during dynamic exercise.
• To determine if eNOS in the NTS mediates the exercise-induced attenuation of sBRS.

Main Methods:

• Conscious Wistar rats were instrumented with radiotelemetry to monitor arterial pressure and heart rate.
• sBRS was assessed using a time-series method before and during dynamic exercise (wheel running).
• Experiments involved sino-aortic denervation and manipulation of eNOS activity in the NTS via adenoviral vectors.

Main Results:

• Dynamic exercise significantly increased systolic blood pressure and heart rate while significantly decreasing sBRS.
• Sino-aortic denervation amplified the rise in systolic blood pressure during exercise but did not affect heart rate changes.
• Disabling eNOS activity in the NTS increased resting sBRS, but the sBRS during exercise remained unchanged compared to controls.

Conclusions:

• Dynamic exercise attenuates sBRS in normotensive rats.
• The baroreceptor reflex limits the rise in arterial pressure during exercise.
• Attenuation of sBRS during dynamic exercise is not mediated by changes in eNOS activity within the NTS.