Tragus Nerve Stimulation Suppresses Post-Infarction Ventricular Arrhythmia by Modulating Autonomic Activity and Heterogeneities of Cardiac Receptor Distribution

Figures

• 

  Figure 1. The study protocol for Panel A was performed with a particular flow chart. From left to right sequentially, Panel B showed the location of tragus stimulation and where to place the 2 alligator clips, the detailed anatomy of auricular branch of vagus nerve and the anatomical location of the subordinate cardiac branch of left stellate ganglion (LSG) for neural recording.

• 

  Figure 2. Typical ST segment elevation images and spontaneous VA images from AMI models containing PVC, VT and VF are indicated in Panels A–D. Results of average heart rate analysis and VAs burden were showed in Panels E–G successively. # P<0.05 compared with the control group, $ P<0.01 compared with the control group. HRV results were recorded weekly from the baseline to the fourth week after AB-VNS (Panels H–J). # P<0.05 between the 2 groups at each point in time. LF– low frequency norm; HF – high frequency norm; LF/HF – low frequency norm/high frequency norm. VA – ventricular arrhythmia; AMI – acute myocardial infarction; PVC – premature ventricular contraction; VT – ventricular tachycardia; VF – ventricular fibrillation; HRV – heart rate variability; AB-VNS – auricular branch of the vagus nerve stimulation.

• 

  Figure 3. Neural discharge was recorded from ICSN and CVN at baseline status (Panels A, B), post-infarction 30 minutes (Panels C, D) and after AB-VNS for 4 weeks (Panels E, F). Typical ECG and neural recording images were shown above. Black arrows indicated the appearance of spontaneous PVC. Panels G, H showed quantitative statistical results of nerve discharge RMS in 3 conditions, including baseline level and the post-MI 30 minutes and after AB-VNS for 4 weeks. # P<0.05 compared with the control group. VN – discharge of vagus nerve; SN – discharge of inferior cardiac sympathetic nerve. ICSN – inferior cardiac sympathetic nerve; CVN – cervical vagal nerve; AB-VNS – auricular branch of the vagus nerve stimulation; ECG – electrocardiograms; PVC – premature ventricular contraction; RMS – root mean square; MI – myocardial infarction.

• 

  Figure 4. Line graphs (Panels A, B) show the variation trend of the EPI and NE concentrations of plasma, which were measured in 3 different periods: baseline, acute MI phase, and after AB-VNS for 4 weeks. (Panels C, D) The EPI and NE concentrations in tissue were determined at 3 sites: peri-MI, non-MI area, and RV, # P<0.05 compared with the control group, $ P<0.01 compared with the control group. EPI – epinephrine; NE – norepinephrine; MI – myocardial infarction; peri-MI – peripheral myocardial infarction; non-MI – non-myocardial-infarction; AB-VNS – auricular branch of the vagus nerve stimulation; RV – right ventricle.

• 

  Figure 5. The density of tyrosine hydroxylase (TH)-positive and choline acetyl transferase (ChAT)-positive nerve fibers were depicted in Panels A, B sampled in 3 regions: LV – left ventricle; ICSN – inferior cardiac sympathetic nerve; CVN – cervical vagus nerve; AB-VN – auricular branch of the vagus nerve. $ P<0.01 compared with the control group, # P<0.05 compared with the control group.

• 

  Figure 6. Immunoblotting measurement of sympathetic nerve-related protein (β1-AR, adrenergic receptor β1) and NGFs (P75NTR, TrkA) were performed by western blot (shown in Panel A). GAPDH was the internal reference. Quantitative statistical analysis results were displayed in Panels B–D. All tissues were from 2 sampling sites: peri-MI – peripheral myocardial infarction area; non-MI – non-myocardial-infarction area. $ P<0.01 compared with the control group.

• 

  Figure 7. The mRNA levels of autonomic nerve efferent receptors were measured by qRT-PCR in the peripheral MI region (peri-MI), non-MI area (non-MI) and right ventricle (RV), and Panels A–C showed the statistical results between the control group and AB-VNS group. $ P<0.01 compared with the control group. qRT-PCR – quantitative real-time polymerase chain reaction; MI – myocardial infarction; peri-MI – peripheral-MI; AB-VNS – auricular branch of the vagus nerve stimulation.