Closed-loop identification of carotid sinus baroreflex transfer characteristics using electrical stimulation

Area of Science:

• Cardiovascular Physiology
• Autonomic Nervous System Research
• System Identification in Biology

Background:

• Estimating carotid sinus baroreflex dynamics typically requires invasive arterial catheterization for aortic pressure perturbation.
• This invasive method limits its application in freely moving animal studies, hindering dynamic characteristic analysis.
• A non-invasive, closed-loop system identification method is needed to overcome these limitations.

Purpose of the Study:

• To develop and validate a closed-loop system identification method using electrical stimulation for baroreflex analysis.
• To estimate the neural and peripheral arc transfer functions of the baroreflex without invasive aortic pressure perturbation.
• To assess the applicability of this method in anesthetized rabbits.

Main Methods:

• Electrical stimulation of the aortic depressor nerve with binary white noise sequence (0-10 Hz) in vagotomized rabbits.
• Measurement of cardiac sympathetic nerve activity (SNA) and aortic pressure (AOP) under closed-loop baroreflex conditions.
• Application of intermittent rapid pacing to estimate the neural arc transfer function.

Main Results:

• The peripheral arc transfer function (SNA to AOP) was accurately modeled as a second-order low-pass filter, with parameters consistent with open-loop methods.
• The neural arc transfer function (AOP to SNA) was modeled as a first-order high-pass filter, also showing consistency with open-loop estimations.
• Fitted parameters for both arcs showed no significant difference between the closed-loop electrical stimulation method and traditional open-loop methods.

Conclusions:

• Closed-loop system identification using electrical stimulation is an effective and less invasive method for estimating baroreflex neural and peripheral arc transfer functions.
• This technique offers a viable alternative to invasive methods, expanding the possibilities for baroreflex studies in dynamic, freely moving animal models.
• The findings support the use of this method for advancing our understanding of cardiovascular regulation.