title: Non-invasive vagus nerve stimulation in healthy humans reduces sympathetic nerve activity.
abstract: BACKGROUND
  Vagus nerve stimulation (VNS) is currently used to treat refractory epilepsy and is being investigated as a potential therapy for a range of conditions, including heart failure, tinnitus, obesity and Alzheimer's disease. However, the invasive nature and expense limits the use of VNS in patient populations and hinders the exploration of the mechanisms involved.
  
  
  OBJECTIVE
  We investigated a non-invasive method of VNS through electrical stimulation of the auricular branch of the vagus nerve distributed to the skin of the ear--transcutaneous VNS (tVNS) and measured the autonomic effects.
  
  
  METHODS
  The effects of tVNS parameters on autonomic function in 48 healthy participants were investigated using heart rate variability (HRV) and microneurography. tVNS was performed using a transcutaneous electrical nerve stimulation (TENS) machine and modified surface electrodes. Participants visited the laboratory once and received either active (200 μs, 30 Hz; n = 34) or sham (n = 14) stimulation.
  
  
  RESULTS
  Active tVNS significantly increased HRV in healthy participants (P = 0.026) indicating a shift in cardiac autonomic function toward parasympathetic predominance. Microneurographic recordings revealed a significant decrease in frequency (P = 0.0001) and incidence (P = 0.0002) of muscle sympathetic nerve activity during tVNS.
  
  
  CONCLUSIONS
  tVNS can increase HRV and reduce sympathetic nerve outflow, which is desirable in conditions characterized by enhanced sympathetic nerve activity, such as heart failure. tVNS can therefore influence human physiology and provide a simple and inexpensive alternative to invasive VNS.
authors.affiliation: School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Clancy
authors.affiliation: School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Mary
authors.affiliation: School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Klaus K
authors.initials: KK
authors.lastname: Witte
authors.affiliation: School of Medicine, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: John P
authors.initials: JP
authors.lastname: Greenwood
authors.affiliation: School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Susan A
authors.initials: SA
authors.lastname: Deuchars
authors.affiliation: School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK. Electronic address: J.Deuchars@leeds.ac.uk.
authors.forename: Jim
authors.initials: J
authors.lastname: Deuchars
mesh_terms: D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D056152:Respiratory Rate / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D004561:Transcutaneous Electric Nerve Stimulation; D014630:Vagus Nerve / Q000502:physiology*; D055815:Young Adult
keywords: Neuromodulation; Sympathetic nervous system; Vagus nerve stimulation