A single baroreceptor unit consists of multiple sensors

Area of Science:

• Cardiovascular Physiology
• Neuroscience
• Cell Biology

Background:

• Arterial baroreceptors (BRs) are crucial for regulating the cardiopulmonary system.
• Previous understanding suggested a single axon connected to one baroreceptor (one-sensor theory).
• Recent findings in airway mechanosensory units indicate multiple sensors per unit (multiple-sensor theory).

Purpose of the Study:

• To investigate if the multiple-sensor theory applies to arterial baroreceptor units.
• To elucidate the subcellular operation of arterial baroreceptors.

Main Methods:

• Morphological analysis of rabbit aortic arch using Na+/K+-ATPase and myelin basic protein antibodies.
• Electrophysiological recordings of single-unit activity from aortic baroreceptors in anesthetized rabbits.
• Examination of unit response to phenylephrine-induced blood pressure changes.

Main Results:

• Morphological studies revealed baroreceptor structures in compact clusters, with single axons connecting to multiple sensors forming a network.
• Electrophysiological recordings showed increased unit activity with rising blood pressure.
• A subset of baroreceptor units exhibited a decrease in activity after sustained high blood pressure, indicating deactivation post-over-excitation.

Conclusions:

• Morphological and physiological data support the multiple-sensor theory for arterial baroreceptor units.
• This finding suggests a more complex neural network for blood pressure sensing than previously understood.
• Baroreceptor units can deactivate after prolonged high-pressure stimulation.