Basic Research
The regulating effect of auricle electrical stimulation on the cardiac vagus nerve in rats
Haiyuan Lu, Di Su, Jie Zhang, Xiaoyuan Jin, Yuemei Hou
Published 2019-06-25
Cite as Chin J Phys Med Rehabil, 2019, 41(6): 401-406. DOI: 10.3760/cma.j.issn.0254-1424.2019.06.001
Abstract
ObjectiveTo compare the regulating effect of electrically stimulating different parts of the auricle on the cardiac vagus nerve in rats, and to explore the basic neural mechanism.
MethodsThe tragus, concha auriculae and helix of 24 male Sprague-Dawley rats were stimulated at different intensities (0-16 mA) and with different durations (0-15 min) and any changes in the heart rate were observed. One week later, the rats were randomized into a tragus injection group, a concha auriculae injection group, a helix injection group and a control group, each of 6. The rats of the first three groups were injected with 2 μL of cholera toxin subunit B conjugate AF555 (CTB-AF555) at the right auricle, while the control group was injected with the same amount of aseptic phosphate-buffered saline at the right tragus. Five days later, all of the rats were sacrificed and their right superior and inferior ganglia and the whole bulbus medullae were resected to observe the fluorescent labeling sites.
ResultsThe rats′ heart rate declined with longer and more intense stimulation of the tragus or concha auriculae, but not with stimulation of the helix. With stimulation of the same duration, a significant decrease was observed in the heart rate when the tragus and concha auriculae were stimulated at 10, 12, 14 or 16 mA compared with when the helix was stimulated at the same intensities. The heart rate when the concha auriculae was stimulated at 12 mA was significantly slower than when the tragus was stimulated at the same intensity. At identical stimulus intensities, the heart rate slowed significantly more when the tragus was stimulated for 6 to 15 minutes and the concha auriculae for 4 to 15 minutes compared with stimulating the helix for the same length of time. And compared with stimulating the tragus for 6 to 10 minutes, the heart rate decreased significantly more when the concha auriculae was stimulated for the same length of time. All of the rats in the tragus and concha auriculae injection groups displayed nerve tracer in their superior and inferior ganglia. In the tragus injection group, CTB-AF555 was observed in the nucleus tractus solitarius (NTS) of 3 of the 6 rats. In the concha auriculae injection group it was observed in 4 of the 6. In the helix injection group, CTB-AF555 was observed in the nucleus of the spinal tract in 5 of the 6 rats, but no nerve tracer was found in their superior or inferior ganglia or in the NTS.
ConclusionElectrical stimulation of the tragus and concha auriculae can regulate the functioning of the cardiac vagus nerve, but stimulating the helix cannot. This is partly because the nerve signals in tragus or concha auriculae stimulation and the cardiac sensory nerve signal are integrated in the inferior ganglion and then analyzed and processed in the bulbar center to monitor the heart.
Key words:
Electrical stimulation; Auricle; Vagus nerve; Heart rate
Contributor Information
Haiyuan Lu
The Third Clinical Medical College, Southern Medical University, Guangzhou 510515, China
Department of Geratology, The Affiliated Fengxian Central Hospital of Southern Medical University, Shanghai 201499, China
Di Su
School of Chemistry &
Chemical Engineering, Shanghai Jiao Tong University, Shanghai 201499, China
Jie Zhang
Department of Geratology, The Affiliated Fengxian Central Hospital of Southern Medical University, Shanghai 201499, China
Xiaoyuan Jin
Department of Geratology, The Affiliated Fengxian Central Hospital of Southern Medical University, Shanghai 201499, China
Yuemei Hou
The Third Clinical Medical College, Southern Medical University, Guangzhou 510515, China
Department of Geratology, The Affiliated Fengxian Central Hospital of Southern Medical University, Shanghai 201499, China
