Aortic arch reflex control of total systemic vascular capacity

Area of Science:

• Cardiovascular Physiology
• Baroreceptor Reflexes
• Autonomic Nervous System Regulation

Background:

• Baroreceptors in the aortic arch and carotid sinus are crucial for regulating blood pressure.
• Understanding the differential contributions of these baroreceptors to vascular capacity is essential for cardiovascular research.

Purpose of the Study:

• To compare the effects of aortic arch baroreceptor stimulation with carotid sinus baroreceptor stimulation on systemic vascular capacity and arterial pressure.
• To investigate potential interactions between aortic arch and carotid sinus baroreceptor reflexes.

Main Methods:

• Anesthetized dogs (n=7) underwent constant flow perfusion.
• Aortic arch and carotid sinus pressures were isolated and manipulated independently.
• Changes in systemic vascular capacity (via reservoir volume) and mean arterial pressure were measured.

Main Results:

• Aortic arch baroreceptor stimulation resulted in a mean vascular capacity change of 1.9 ± 0.2 ml/kg and arterial pressure change of 18.7 ± 3.7 mmHg.
• Carotid sinus baroreceptor stimulation yielded a mean vascular capacity change of 7.2 ± 0.9 ml/kg and arterial pressure change of 45.1 ± 4.1 mmHg.
• Neither reflex's response was significantly influenced by the pressure level of the other baroreceptor area.

Conclusions:

• Carotid sinus baroreceptors exhibit a greater influence on systemic vascular capacity and arterial pressure compared to aortic arch baroreceptors.
• The baroreflexes from the aortic arch and carotid sinus appear to operate independently in terms of their effects on vascular capacity.