Pain is reduced by transcutaneous cervical vagus nerve stimulation and correlated with cardiorespiratory variability measures in the context of opioid withdrawal

Effects of transcutaneous auricular vagus nerve stimulation at left cymba concha on experimental pain as assessed with the nociceptive withdrawal reflex, and correlation with parasympathetic activity

The aim of this study was to clarify the effects of transcutaneous auricular vagus nerve stimulation (taVNS) to the left cymba concha on the pain perception using nociceptive withdrawal reflex (NWR), which is known to be associated with chronic pain, and to investigate whether there is a relationship between taVNS-induced suppression of the NWR and parasympathetic activation. We applied either 3.0 mA, 100 Hz taVNS for 120 s on the left cymba concha (taVNS condition) or the left earlobe (Sham condition) for 20 healthy adults. NWR threshold was measured before (Baseline), immediately after (Post 0), 10 min (Post 10) and 30 min after (Post 30) stimulation. The NWR threshold was obtained from biceps femoris muscle by applying electrical stimulation to the sural nerve. During taVNS, electrocardiogram was recorded, and changes in autonomic nervous activity measured by heart rate variability (HRV) were analyzed. We found that the NWR thresholds at Post 10 and Post 30 increased compared with baseline in the taVNS group (10 min after: p = .008, 30 min after: p = .008). In addition, increased parasympathetic activity by taVNS correlated with a greater increase in NWR threshold at Post 10 and Post 30 (Post 10: p = .003; Post 30: p = .001). The present results of this single-blinded study demonstrate the pain-suppressing effect of taVNS on NWR threshold and suggest that the degree of parasympathetic activation during taVNS may predict the pain-suppressing effect of taVNS after its application.

Noninvasive Vagal Nerve Stimulation for Opioid Use Disorder

Background

Opioid Use Disorder (OUD) is an escalating public health problem with over 100,000 drug overdose-related deaths last year most of them related to opioid overdose, yet treatment options remain limited. Non-invasive Vagal Nerve Stimulation (nVNS) can be delivered via the ear or the neck and is a non-medication alternative to treatment of opioid withdrawal and OUD with potentially widespread applications.

Methods

This paper reviews the neurobiology of opioid withdrawal and OUD and the emerging literature of nVNS for the application of OUD. Literature databases for Pubmed, Psychinfo, and Medline were queried for these topics for 1982-present.

Results

Opioid withdrawal in the context of OUD is associated with activation of peripheral sympathetic and inflammatory systems as well as alterations in central brain regions including anterior cingulate, basal ganglia, and amygdala. NVNS has the potential to reduce sympathetic and inflammatory activation and counter the effects of opioid withdrawal in initial pilot studies. Preliminary studies show that it is potentially effective at acting through sympathetic pathways to reduce the effects of opioid withdrawal, in addition to reducing pain and distress.

Conclusions

NVNS shows promise as a non-medication approach to OUD, both in terms of its known effect on neurobiology as well as pilot data showing a reduction in withdrawal symptoms as well as physiological manifestations of opioid withdrawal.