Effect of Transcutaneous Auricular Vagus Nerve Stimulation on Protracted Alcohol Withdrawal Symptoms in Male Alcohol-Dependent Patients

Transcutaneous auricular vagus nerve stimulation modifies cortical excitability in middle-aged and older adults

There is a growing interest in the clinical application of transcutaneous auricular vagus nerve stimulation (taVNS). However, its effect on cortical excitability, and whether this is modulated by stimulation duration, remains unclear. We evaluated whether taVNS can modify excitability in the primary motor cortex (M1) in middle-aged and older adults and whether the stimulation duration moderates this effect. In addition, we evaluated the blinding efficacy of a commonly reported sham method. In a double-blinded randomized cross-over sham-controlled study, 23 healthy adults (mean age 59.91 ± 6.87 years) received three conditions: active taVNS for 30 and 60 min and sham for 30 min. Single and paired-pulse transcranial magnetic stimulation was delivered over the right M1 to evaluate motor-evoked potentials. Adverse events, heart rate and blood pressure measures were evaluated. Participant blinding effectiveness was assessed via guesses about group allocation. There was an increase in short-interval intracortical inhibition (F = 7.006, p = .002) and a decrease in short-interval intracortical facilitation (F = 4.602, p = .014) after 60 min of taVNS, but not 30 min, compared to sham. taVNS was tolerable and safe. Heart rate and blood pressure were not modified by taVNS (p > .05). Overall, 96% of participants detected active stimulation and 22% detected sham stimulation. taVNS modifies cortical excitability in M1 and its effect depends on stimulation duration in middle-aged and older adults. taVNS increased GABAAergic inhibition and decreased glutamatergic activity. Sham taVNS protocol is credible but there is an imbalance in beliefs about group allocation.

Clinical application of transcutaneous auricular vagus nerve stimulation: a scoping review

PURPOSE

Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulation therapy. This study aimed to explore the therapeutic use of taVNS, optimal stimulation parameters, effective sham protocols, and safety.

METHODS

A scoping review was conducted. Five databases and grey literature were searched. The data extracted included stimulation parameters, adverse events (AEs), and therapeutic effects on clinical outcomes.

RESULTS

109 studies were included. taVNS was used across 21 different clinical populations, most commonly in psychiatric, cardiac, and neurological disorders. Overall, 2,214 adults received active taVNS and 1,017 received sham taVNS. Reporting of stimulation parameters was limited and inconsistent. taVNS appeared to have a favourable therapeutic effect across a wide range of clinical populations with varied parameters. Three sham protocols were reported but their effectiveness was documented in only two of the 54 sham-controlled studies. Most reported adverse events were localised to stimulation site.

CONCLUSION

There is growing evidence for taVNS therapeutic effect. taVNS appears safe and tolerable. Sham protocols need evaluation. Standardised and comprehensive reporting of both stimulation parameters and adverse events is required. Two different questionnaires have been proposed to evaluate adverse events and the effectiveness of sham methods in blinding participants.

Transcutaneous auricular vagus nerve stimulation in the treatment of disorders of consciousness: mechanisms and applications

This review provides an in-depth exploration of the mechanisms and applications of transcutaneous auricular vagus nerve stimulation (taVNS) in treating disorders of consciousness (DOC). Beginning with an exploration of the vagus nerve's role in modulating brain function and consciousness, we then delve into the neuroprotective potential of taVNS demonstrated in animal models. The subsequent sections assess the therapeutic impact of taVNS on human DOC, discussing the safety, tolerability, and various factors influencing the treatment response. Finally, the review identifies the current challenges in taVNS research and outlines future directions, emphasizing the need for large-scale trials, optimization of treatment parameters, and comprehensive investigation of taVNS's long-term effects and underlying mechanisms. This comprehensive overview positions taVNS as a promising and safe modality for DOC treatment, with a focus on understanding its intricate neurophysiological influence and optimizing its application in clinical settings.

Involvement of the Dorsal Vagal Complex in Alcohol-Related Behaviors

The neurobiological mechanisms that regulate the development and maintenance of alcohol use disorder (AUD) are complex and involve a wide variety of within and between systems neuroadaptations. While classic reward, preoccupation, and withdrawal neurocircuits have been heavily studied in terms of AUD, viable treatment targets from this established literature have not proven clinically effective as of yet. Therefore, examination of additional neurocircuitries not classically studied in the context of AUD may provide novel therapeutic targets. Recent studies demonstrate that various neuropeptides systems are important modulators of alcohol reward, seeking, and intake behaviors. This includes neurocircuitry within the dorsal vagal complex (DVC), which is involved in the control of the autonomic nervous system, control of intake of natural rewards like food, and acts as a relay of interoceptive sensory information via interactions of numerous gut-brain peptides and neurotransmitter systems with DVC projections to central and peripheral targets. DVC neuron subtypes produce a variety of neuropeptides and transmitters and project to target brain regions critical for reward such as the mesolimbic dopamine system as well as other limbic areas important for the negative reinforcing and aversive properties of alcohol withdrawal such as the extended amygdala. This suggests the DVC may play a role in the modulation of various aspects of AUD. This review summarizes the current literature on neurotransmitters and neuropeptides systems in the DVC (e.g., norepinephrine, glucagon-like peptide 1, neurotensin, cholecystokinin, thyrotropin-releasing hormone), and their potential relevance to alcohol-related behaviors in humans and rodent models for AUD research. A better understanding of the role of the DVC in modulating alcohol related behaviors may lead to the elucidation of novel therapeutic targets for drug development in AUD.