Effect of transcutaneous vagus nerve stimulation on muscle activity in the gastrointestinal tract (transVaGa): a prospective clinical trial

Non-invasive stimulation of vagal afferents reduces gastric frequency

“…In line with the hypothesized efferent effect, we found that taVNS alters a marker of energy homeostasis in humans. The observed taVNS-induced reduction in gastric frequency is well in line with previous findings linking VNS to altered energy homeostasis [13,14,17]. This efferent effect on gastric motility might be due to a taVNS-induced release of dopamine in the brain stem.…”

“…Although there is preliminary evidence linking vagal signaling and energy homeostasis [14], efferent taVNS-induced effects on digestion and energy metabolism in healthy humans have not been conclusively demonstrated. We therefore investigated whether taVNS vs. sham changes electrogastrography (EGG) and indirect calorimetry as markers of energy homeostasis.…”

“…In rodents, VNS triggered by phasic stomach contractions resulted in weight loss [13]. In humans, taVNS led to a decreased frequency and increased amplitude of gastric motility [14]. Such metabolic effects might be related to VNSinduced increases in the activity of brown adipose tissue, which in turn increased the basal metabolic rate [15].…”

Stimulus frequency modulates brainstem response to respiratory-gated transcutaneous auricular vagus nerve stimulation

“…Thus, subjects with higher responses to 2 Hz RAVANS also showed higher responses to 100 Hz RAVANS in these nuclei. their modulation in response to RAVANS might be due to vagovagal feedback and serve as the basis of therapeutic effects observed for cardiovascular [14,16,48] and gastrointestinal [11,12] taVNS applications. The pre-B€ otzinger complex, a functionallydefined region located ventrally to the NAmb, is known to be a generator for respiratory rhythms in mammals [49], and evoked fMRI response in this nuclei may result from the respiratory-gated nature of RAVANS taVNS, which future studies should explore more explicitly.…”

“…Transcutaneous auricular vagus nerve stimulation (taVNS) has enjoyed renewed interest in recent years since its description almost twenty years ago as a non-invasive approach to vagus nerve stimulation through the auricular branch of the vagus nerve (ABVN). Multiple clinical disorders have been targeted by taVNS researchers, including epilepsy [1], depression [2,3], pain [4e8], stroke [9,10], and various gastrointestinal [11,12] and cardiovascular disorders [13e18]. Importantly, stimulation parameter optimization may differ between these clinical applications, and an objective framework should be explored for optimizing parameter setting for taVNS.…”