Transcutaneous Auricular Vagus Nerve Stimulation and Human Autonomic Function

Introduction: Autonomic dysfunction is associated with the development of numerous chronic diseases. Transcutaneous auricular vagus nerve stimulation (tcAVNS) has emerged as a promising noninvasive therapy for pathologies where autonomic nervous system dysfunction may be implicated. To fully realize the potential of tcAVNS as a therapeutic approach, physiological responses to treatment must be characterized. While previous studies have investigated the impact of tcAVNS on heart rate (HR) and blood pressure (BP), few report muscle sympathetic nerve activity (MSNA) responsiveness to tcAVNS. Further, existing work that includes MSNA is conflicting. The purpose of the current study was to investigate the effect of tcAVNS on resting cardiovascular and sympathetic activity in healthy adults. We hypothesized that HR, BP, and MSNA would decrease in response to acute tcAVNS. Additionally, we hypothesized that cardiovagal baroreflex sensitivity (cvBRS) and sympathetic baroreflex sensitivity (sBRS) would improve with tcAVNS. Methods: Ten participants (5M, 5F; age: 21±2, BMI: 22±3 kg/m 2 ) completed a morning autonomic function test session that recorded HR (electrocardiogram), BP (finger plethysmography), and MSNA (microneurography). Using a randomized, crossover design, each participant underwent a 10-minute resting baseline followed by 10 minutes of sham or active tcAVNS (intensity: 1.8±1.0 mA). Participants were tested on the same day, separated by ~45 minutes between conditions. Quality MSNA signals were established throughout the entire protocol in 6 participants. Average mean arterial pressure (MAP), HR, MSNA burst frequency (BF) and burst incidence (BI), heart rate variability (HRV), cvBRS, and sBRS were quantified during baseline and stimulation within each experimental condition. Results: There were no demonstrable time, condition, or interaction effects (all p>0.05) on any cardiovascular or autonomic variables. Similar responses to sham and active stimulation were observed for MAP (sham: Δ1.1±2.0 mmHg, active: Δ1.0±1.3 mmHg, p>0.05), HR (sham: Δ-0.5±0.9 bpm, active: Δ-1.5±0.4 bpm, p>0.05), high frequency HRV (HF; sham: Δ-53±301 ms 2 , active: Δ42±247 ms 2 , p>0.05), root mean square of successive differences (RMSSD; sham: Δ0.9±2.0 ms, active: Δ-0.1±3.0 ms, p>0.05), cvBRS up-up sequences (sham: Δ1.1±3.8 ms/mmHg, active: Δ1.1±1.1 ms/mmHg, p>0.05), and cvBRS down-down sequences (sham: Δ2.0±1.5 ms/mmHg, active: Δ2.2±2.1 ms/mmHg, p>0.05). Similarly, MSNA BF (sham: Δ1.4±0.0 bursts/min, active: Δ-0.2±1.1 bursts/min, p>0.05), MSNA BI (sham: Δ2.4±0.9 bursts/100hb, active: Δ0.0±1.9 bursts/100hb, p>0.05), and sBRS (sham: Δ-0.3±0.1 bursts/100hb/mmHg, active: Δ-0.7±0.3 bursts/100hb/mmHg, p>0.05) responses were comparable during sham and active stimulation compared to baseline. Conclusion: These preliminary results suggest that tcAVNS has minimal influence on resting autonomic and cardiovascular regulation in healthy young adults. Further research is needed to fully characterize the autonomic response to tcAVNS, and to establish the potential of tcAVNS to influence autonomic function during other behavioral states, such as stress and sleep. Funding: Baylor University Department of Health, Human Performance, and Recreation Thesis Research Grant This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.