The effect of non-invasive transauricular vagus nerve stimulation on upper gastrointestinal motility in healthy individuals

Although motor function in the GI tract is intrinsically regulated by pacemaker
cells of the enteric nervous system, there is a strong extrinsic influence via
the efferent vagus. Motor responses in the upper GI tract, which is innervated
by the vagus nerve, are characterized by stereotypical motility patterns called
the migrating motor complex (MMC). Gastrointestinal rumbling, which is mainly
noticed during fasting, is associated with the MMC. The MMC is an aborally
propagating contractility complex during the fasting state, characterized by
three different phases: phase I is a period of motor quiescence, phase II
displays progressively increasing motor activity and phase III has the highest
contractile activity and can start in either the stomach or small intestine.
The MMC moves from the stomach to the terminal ileum over a period of 1.5-2.0*
hours and is interrupted by nutrient intake, after which the motor response
switches to a less coordinated *fed pattern,* which usually lasts at least 2
hours after meal ingestion before the MMC returns. The vagus nerve plays an
important role in the initiation of MMC that originate from the stomach, as
vagotomy was shown to block MMCs. In addition, acute stress has been shown to
inhibit MMCs.
Whether a disturbance in upper GI tract motility has a role in the development
of abdominal symptoms remains a subject of debate. In this study, we aim to
investigate whether tVNS is able to induce migrating motor complexes as a
result of stimulation of the vago-vagal intestinal reflex loop in healthy
subjects.

To study the impact of tVNS on gut motor function, in particular with regards
to its potential to induce phase III contractions in the upper GI tract, in
healthy subjects.

This is an intervention study with 12 healthy volunteers, aged 18-55 years old.

During the eight-hour measurement period, one block of four hours will consist
of tVNS, and one block of 4 hours will consist of sham-tVNS.

Participants will not benefit from participating in this study.
Insertion of the antroduodenal manometry catheter can be uncomfortable, but in
most patients this feeling disappears after a few minutes. After the manometry
patients can have a slight irritation of the nose or throat. The radiation
exposure associated with fluoroscopy during the positioning of the catheter is
minimal, with a total radiation exposure of approximately 0.05-1 mSv.
The collection of blood samples can bring along some slight risks, i.e.
hematoma, bleeding, pain and/or vasovagal reaction during or after vena
punction. Subjects will be seated on an examination bed, to prevent side
effects to occur.
Participation in this study will cost some time. Subjects have to visit the
hospital twice. The screening will take around 30-45 minutes. And the second
visit will take around 9-10 hours.