Randomized, double-blind trial to investigate the influence of a single 4 hours episode of transcutaneous vagal nerve stimulation on the expression of microRNA, various cytokines, chemokines, neuropeptides, cerebral resting state and gastric motility in healthy volunteers.

Transcutaneous vagal nerve stimulation (tVNS) is a non-invasive treatment option for epilepsy. TVNS works via electrical stimulation of the vagal nerve in the outer ear area via two steel electrodes and is performed for about 4 hours per day. Its mechanism of action is unknown. We hypothesize that expression of microRNA (miRNA), and/or release of cytokines, chemokines or neuropeptides is involved in the anticonvulsant activity. TVNS might also influence the cerebral resting state as measured by functional magnetic resonance imaging (fMRI). Due to it's anatomical connections, stimulation of the vagal nerve may furthermore result in altered gastric motility.

This study aims to detect levels of miRNA, cytokines, chemokines and neuropeptides in the blood of healthy volunteers before and after 4 hours of conventional tVNS or sham tVNS. Cerebral resting state and gastric motility will be measured by fMRI.

To this end, 60 healthy volunteers will be recruited and divided into 2 groups. 30 healthy volunteers will be treated with tVNS (25 Hz) for 4 hours (tVNS group). 30 healthy volunteers will be treated with sham tVNS (1 Hz) for 4 hours (control group).

On day 1 of the study, participants will be randomized to one of the two groups. Blood will be drawn from all participants at baseline. Both groups receive a standardized breakfast. TVNS ear electrodes will be put into place for 4 hours without electrical stimulation. Thereafter, blood will be drawn.

On day 2 of the study, blood will be drawn, and all participants receive a standardized breakfast again. Afterwards, tVNS (25 Hz) will be performed in participants of the tVNS group, and sham tVNS (1 Hz) will be performed in participants of the control group. TVNS or sham tVNS end after 4 hours. Blood will be drawn immediately after stimulation end. Thereafter, MRI will be performed in all participants (fMRT resting state, gastric motility). This ends the study for the participant.

Inclusion Criteria:

• Age between 18 and 65 years
• Written informed consent

Exclusion Criteria:

• pregnancy
• active implants (like cardiac pacemaker, cochlea implant, implanted VNS)
• contraindications for MRI (e. g. metal fragments, claustrophobia)
• skin lesions in the ara of the left ear conch
• nickel allergy
• drug or alcohol abuse
• current acute disease or medical history of chronic disease
• participant is under legal guardianship