ABSTRACT
OBJECTIVE: Hypertension is the largest threat to patient health and a burden to health care systems. Despite various options, 30% of patients do not respond sufficiently to medical treatment. Mechanoreceptors in the aortic arch relay blood pressure (BP) levels through vagal nerve (VN) fibers to the brainstem and trigger the baroreflex, lowering the BP. Selective electrical stimulation of these nerve fibers reduced BP in rats. However, there is no technique described to localize and stimulate these fibers inside the VN without inadvertent stimulation of non-baroreceptive fibers causing side effects like bradycardia and bradypnea. APPROACH: We present a novel method for selective VN stimulation to reduce BP without the aforementioned side effects. Baroreceptor compound activity of rat VN (n = 5) was localized using a multichannel cuff electrode, true tripolar recording and a coherent averaging algorithm triggered by BP or electrocardiogram. MAIN RESULTS: Tripolar stimulation over electrodes near the barofibers reduced the BP without triggering significant bradycardia and bradypnea. The BP drop was adjusted to 60% of the initial value by varying the stimulation pulse width and duration, and lasted up to five times longer than the stimulation. SIGNIFICANCE: The presented method is robust to impedance changes, independent of the electrode's relative position, does not compromise the nerve and can run on implantable, ultra-low power signal processors.
Subject(s)
Blood Pressure/physiology , Electrodes, Implanted , Feedback, Physiological/physiology , Pressoreceptors/physiology , Vagus Nerve Stimulation/instrumentation , Vagus Nerve Stimulation/methods , Vagus Nerve/physiology , Animals , Equipment Design , Equipment Failure Analysis , Male , Miniaturization , Rats , Rats, Wistar , Vagus Nerve Stimulation/adverse effectsABSTRACT
Electrical stimulation of afferent nerve fibers originating from pressure sensors can trigger the baroreflex to reduce blood pressure and might be an alternative to treat patients with hypertension. In this study, baroreceptor compound activity was detected using multi-channel cuff-electrode recordings on rat vagal nerve. In order to isolate the vagal nerve signals from external potentials (such as ECG- and EMG-coupling), a tripolar measuring technique was applied. To eliminate noise and neural signals corresponding to other organs, coherent averaging was used. The baroreceptor-correlated signals appear predominantly in one of the electrode channels, presumably close to the corresponding neural substrate. This localization was done in real-time.
