In addition to the superordinate regulation by means of the mesencephalic periaqueductal grey, the neurovegetative system - including vagus activity - is essential in the regulation of stress reactions. This paper explains, discusses and presents essential study results and correlations, dysfunction mechanisms, diagnostics and osteopathic treatment approaches and techniques as well as self-management approaches for the regulation of the vagus.
Vagal mechanisms of action, vagus dysfunction, diagnosis and interpretation of vagus activity, self-help approaches, osteopathic vagus nerve stimulation (VNS), mesencephalic periaqueductal grey, psychosomatic osteopathy.
Besides the superordinate regulation by means of the mesencephalic periaqueductal grey, the neurovegetative - among others the vagus activity - is essential in the regulation of stress reactions. This article explains, discusses and presents essential study results and correlations, dysfunction mechanisms, diagnostics and osteopathic treatment approaches and techniques as well as self-management approaches for the regulation of the vagus.
vagal mechanisms of action, vagus dysfunction, diagnosis and interpretation of vagus activity, self-help approaches, osteopathic vagus nerve stimulation (VNS), mesencephalic periaqueductal grey, psychosomatic osteopathy
Superordinate behavioural states such as fight and flight, immobilisation or freezing state and risk assessment - with the associated motor, autonomic and endocrine effects - are coordinated by the mesencephalic periaqueductal grey (PAG) , , , . In this process, vagal afferents are transmitted through the nucleus tractus solitarii to the PAG, hypothalamus, amygdala as well as to the insular, cingulate and prefrontal cortex, where they are integrated into emotional and cognitive processes , , , .
Even though popular polyvagal theory does not adequately account for these anatomical features and mechanisms of action, the vagus is nevertheless highly significant , . Thus, subdiaphragmatic vagal afferents appear to influence innate fear, learned fear and other behaviours , . In addition, vagal afferents modulate spinal nociceptive processes in various experimental models , .
Evolutionarily, the autonomic nervous system regulated and still regulates the maintenance of the most important bodily functions. Prey animals, for example, reacted to danger from predators by freezing and shutting down their metabolism. This behaviour was regulated by the parasympathetic nervous system, which prioritised such behaviour over metabolic functions if necessary. This clearly shows how the survival of the organism as a whole is hierarchically regulated in regulatory systems. from individual organ functions. The sympathetic nervous system developed in connection with flight instead of freezing behaviour as well as hunting instinct and fight control mechanisms. This manifests itself in pupil dilation (better twilight vision and sharper peripheral vision), dilation of the limb and lung blood vessels (necessary for flight and fight behaviour) and an increase in stress hormones for faster reactions and glucose supply. Here, too, the focus is on the whole organism and not exclusively on the functioning of individual organs.
The parasympathetic and sympathetic nervous systems do not necessarily act antagonistically. Unmyelinated fibres, mainly originating from the dorsalis nervi vagi nerve, regulate blood flow and activity of the abdominal organs, while myelinated fibres, originating from the ambiguus nerve, regulate the thoracic organs of the heart and lungs as well as speech (superior laryngeal and recurrent nerve) and the hearing of human speech (including the stapedius nerve after connection with the facial nerve). There are also vagal influences on heart rate variability (HRV), blood sugar control and the immune system, as well as voice pitch, appetite and bronchial function. The vagus nerve acts as a link between the peripheral autonomic nervous system and the brain. It also facilitates the storage of memories. Vagus nerve stimulation has been shown to have brain plasticity and memory enhancing effects .
Afferents exist in particular from the intestine and other abdominal organs. Thus, afferent fibres of the vagus nerve metabolically influence the microglia of the brain .. Normally, the central nervous system is protected by the blood-brain barrier. However, it can potentially be damaged by the vagus, in that efferent from the gastrointestinal tract can activate microglia in vagal structures and alter gut-brain communication .
Pathophysiologically, the vagus is important, for example, in headaches, depression and post-traumatic stress disorder (PTSD). In addition, the vagus nerve also has a strong influence on the immune system, heart rate variability, blood sugar control, the development and modulation of headaches (including migraine via serotonin release), our voice pitch, the function of our bronchial tubes, appetite control, the development of depression, etc. , , , , . , , , , .
With increasing age, changes occur at least in the thicker somatomotor vagus fibres, which thin out as they progress .
Decreased vagus activity
- Decreased vagus activity occurs, for example, in autoimmune diseases such as ulcerative colitis, lowered immunity, malabsorption and obesity.
- Hypotonic vagal activity with normotonic activity of the enteric nervous system can occur in alcohol abuse and type 2 diabetes mellitus. In addition to alcohol abstinence, the vagus nerve can be stimulated therapeutically (see below).
- Hypotonic vagal activity with hypotonic activity of the enteric nervous system carries a high risk for neurodegenerative disease patterns. Here, the low immune status should first be improved and the viral load reduced ,  and only then should the vagus nerve be stimulated. In addition, the small intestine region can be stretched to increase myenteric activity , .
Increased vagus activity
The vagus activity can not only be decreased but also increased in a dysfunctional way.
- Increased vagus activity occurs, for example, in allergies, Crohn's disease and obesity.
- In the case of hypertonic vagus activity, OMT can be used to stretch the diaphragm, the radix mesenterii and the high cervical region.
- Increased vagus activity in young people can lead to an increase in gastric acid production, increased gastric emptying and possibly diarrhoea. Here, in addition to manual approaches, the mouth region should be cleaned and the pathogen load reduced.
By sense of smell - Hold lavender essential oil under the nose: Stimulation of the vagus promotes gastric emptying. This is audible, e.g. with the stethoscope in the region of the pylorus. 
By swallowing - Drinking a glass of water serves to test the vagus in the oesophagus (norm about 5 seconds; the swallowing period is reduced in case of decreased activity and e.g. in Parkinson's disease).
By means of HRV measurement - HRV measurement parameters provide insight into the autonomic function of the heart and allow assessments of the functioning of the autonomic nervous system . The vagus nerve conducts information much faster than the sympathetic nervous system. For example, vagus activation of heart rate is up to 8 times faster compared to sympathetic activation, so that fluctuations in heart rate are much more strongly determined by the vagus .
Using the Ruffier-Dickson test to determine hypotonia of the vagus nerve - After 1 minute in supine position measure the pulse beats (P1), perform squats 30× or for 45 seconds, then pulse beats in standing position immediately afterwards (P2) and after 1 minute in supine position measure again (P3).
The Dickson index is used to assess the heart's ability to recover after exercise. This value correlates with HRV, O2max-measurements, lung elasticity, diaphragmatic mobility, gastric emptying and nitric oxide.
Calculation of the Dickson Index
((P2-70) + 2 (P3-P1))/10
10 = poor adaptation.
Other possible indications for reduced vagus activity
- Reduced neck mobility and jaw disorders, CMD (craniomandibular dysfunction).
- Visceral fat: Here, an abdominal circumference measurement can be taken (vagus activity is reduced in overweight, dysfunctionally increased in obesity).
- Compression of the pars descendens of the duodenum with the risk of reflux.
- Positive trigger points of the neck and jaw muscles.
- Tension restrictions in the area of the vagina carotica.
- Positive Gesret's point: This is usually located intercostally under the left axilla, more rarely on the right. The test is positive for tenderness and palpation of a kind of fat ball in this region.
- Viral loads: by blood tests.
- Presence of proprionibacteria in the oral region: Findings by means of UV lamp.
Vagus nerve stimulation (VNS)
For an overview, see also .
Stimulation of the vagus nerve during exposure therapy - as possibly applied in the osteopathic approach of Liem's multimodal bifocal integration - eliminates anxiety, hypervigilance, avoidance behaviour and antisocial behaviour in animal experiments on post-traumatic stress disorder (PTSD) , , , , , , . VNS enhanced the extinction of conditioned fear in experiments on rats without , . and with PTSD , .. VNS can also counteract fear extinction disorders, reduce anxiety-like behaviour, improve other PTSD symptoms  and facilitate conditioned fear responses .
It has also been shown that the number of key molecules that promote synaptic plasticity can be increased by VNS, e.g.. acetylcholine , serotonin , noradrenaline , fibroblast growth factor-1 (FGF-1) and the growth factor BDNF (brain-derived neurotrophic factor) , neurogenesis , Fos (a nuclear protein expressed under conditions of high neuronal activity) , Tropomyosin receptor kinase B (TrkB) , neurexin, cadherin and calcium channels , NMDA-receptors (NMDA = N-methyl-D-aspartate) , .
Transcutaneous electrical vagus nerve stimulation simultaneously shows an improvement in neuronal plasticity, especially in combination with training , ., e.g. in the locus coeruleus ,  and memory consolidation , , .. The combination of VNS with sensory or motor events is able to reorganise the sensory or motor cortex .
The combination of VNS and exposure to unamplified conditioned signals was able to enhance extinction of infralimbic prefrontal cortex - basolateral amygdala signalling pathways in animal experiments , .
There is evidence that VNS should be used in combination with exposure-based approaches to extinguish conditioned fear and that its isolated application is not sufficient .
An autonomic vagovagal loop reaches visceral impulses into the Ncl. tractus solitarii (NTS), which transmits efferents to the Ncl. dorsalis nervi vagi (DMN) to the rostral ventrolateral medulla (RVLM) and to the intermediate lateral medulla (ILM), with the aim of achieving a balance between sympathetic and parasympathetic responses to different physical states. The vagus does not act in isolation. Modulations of the vagovagal loop are triggered by a autonomic forebrain loop possible, via interactions between the NTS and other brain areas such as hypothalamus, amygdala, cingulate cortex, insular cortex, prefrontal cortex, which are also involved in neuroendocrine, emotional and cognitive behavioural controls (see Fig. 1).
Reorganisation of the sensory or motor cortex , post-traumatic stress disorder and anxiety disorders , , , ,  as well as chronic low-threshold inflammation, for anti-inflammation, e.g. rheumatoid arthritis.e.g. in rheumatoid arthritis; anti-tumour necrosis factor α (anti-TNF-α), i.e. anti-inflammatory effect, gastroduodenal emptying disorders, possibly drug-resistant epilepsy, depression .
Vagus stimulation in the craniocervical region according to Liem
- Thumb in the area of the cavum conchae (ramus auricularis nervi vagi)
- Index finger on the anguli mastoideae.
- Middle finger to the mastoids.
- Ring finger and little finger in the area of the atlantooccipital joint (see Fig. 2).
Fig. 2 Legend: Vagus stimulation in the craniocervical region
- The skin in the area of both concha auricularis  is stimulated manually with the thumbs and the auricular branches on the proc. mastoideus are stimulated gently with the middle fingers.
- The index fingers anteriorise the lower jaw.
- The ring finger and little finger exert suboccipital inhibition or decompression in the suboccipital region and near the jugular foramen. Here, not only a vagus-stimulating effect but also an improvement in cerebral blood flow has already been demonstrated , , .
The vagus nerve passes through the middle part of the jugular foramen, caudal to the glossopharyngeal nerve and superficial to the internal jugular vein.
Stimulation can also be done by electrostimulation in the ear area following Bonaz or on the mastoid and below the diaphragm . The vagus can be stimulated on the mastoid and diaphragm with a TENS unit at 10 hertz. Needling is also possible 
Vagus stimulation in the area of the vagina carotica
The vagus nerve can also be gently stimulated in the area of the vagina carotica. The middle fingers of both hands are positioned about 1 cm apart, medial to the sternocleidomastoid muscle - between the common carotid artery and the internal jugular vein, just below the thyroid cartilage. Stimulation in the region of the course of the vagus nerve is by means of craniocaudal gentle mobilisation.
Fig. 3. legend: Vagus stimulation in the area of the vagina carotica
Vagus stimulation in the area of the diaphragm
Medially, the deep diaphragmatic region in the oesophageal area. (Truncus vagalis anterior and posterior). To do this, let the thumbs sink into the depths on both sides of the xiphoid and follow micro-movements in the area of the oesophagus while the other fingers rest on the lower intercostal spaces. At the same time, the patient slows down breathing by about half.
In the second step the Ganglion coeliacum, approximately midway between the navel and the xiphoid, relax (see also Fulford technique , p. 520).
Reorganisation of the sensory or motor cortex
This allows sensory or motor stimuli, movements, postures and functional OMT to be combined with VNS. In addition, VNS is also used within the framework of multimodal bifocal integration according to Liem. When practising osteopathic heart-focused palpation according to Liem, a vagus-stimulating effect could be proven .
Further OMT approaches
Rib raising techniques  and High-Velocity/Low-Amplitude Techniques (HVLAT)  can have a vagus activating effect. A single OMT session in healthy participants already led to a faster recovery of heart rate and sympathovagal balance and prevented the typical rise in cortisol levels after a psychological stressor .
Patients can stimulate the vagus independently by the following measures to reduce stress reactions. These can be used as an adjunct to treatment , :
Deep and slowed breathing with or without HRV feedback , ,  - In a study in which further yogic breathing techniques and kriyas were - these are physical Purification techniques (Ujjayi Breathing, Bhastrika, Sudarshan Kriya) - were practised, it was assumed that these have a parasympathetic activating effect .
Autogenic training , Yoga  and Tai Chi , , ,  are said to have vagal activating effects. However, since there are very different types of yoga, e.g. very calm ones like yin yoga, and at the same time very dynamic types like power yoga, future studies should examine the different forms for their vagal effects.
Meditation ,  - For example, Loving Kindness Meditation increased positive emotions through improved perception of social relationships, which in turn led to an increase in vagal tone. However, this effect was only achieved in those who actually felt increased joy and social connectedness . It is suspected that vagal activation also occurs via deep breathing during meditation . As there are very different types of meditation, just like in yoga, these variations could be taken into account in future studies.
Increase in oxytocin - All interventions that lead to an increase in oxytocin (and vasopressin), such as massage, touch, etc., can be recommended as these improve parasympathetic function , , .
Chanting, humming, mantra singing - Singing increases HRV in healthy 18-year-old women and men. However, this has only been investigated in one study so far. Humming, hymn singing, energetic singing and mantra singing have each been reported to increase HRV in slightly different ways . For example, singing, especially energetic singing, is also said to be simultaneously arousing, but without significant sympathetic activity, possibly because the vagally triggered activity dampens the sympathetic one. This physiological reaction in singing is said to be able to trigger the homeostatic state of flow .
There are two ways in which music could communicate the state of the ANS between singers: Through the laryngeal vocal cord muscles used in singing, mediated by the reccurens nerve of the vagus nerve as well as through a kind of vagal pump stimulated during singing . Chanting the mantra "Om" also activates the vagus. The authors suggest that this may be due to stimulation of its auricular branches . Both mantra and prayer recitation in a study of 23 adults caused an increase in existing cardiovascular rhythms, HRV and a reduction in blood pressure with rhythm formulas involving breathing at 6 breaths per minute . Singing is also said to release oxytocin .
Laughter - in a pilot study on laughter yoga, participants showed improved immediate mood and increased HRV after a laughter intervention .
Pleasant social interaction - Vagal activity increase through the interaction of parental and child positive socialisation .
Cold exposure - Cold showers and other cold interventions increased parasympathetic activity via activation of cholinergic neurons by the vagus nerve , especially when repeatedly exercised over a long period of time. Thus, habituation may be associated with decreased sympathetic and concomitant increased parasympathetic activation during cold exposure . The study in humans was conducted at 10°C cold . Acute cold interventions of 4°C also led to parasympathetic stimulation in animal experiments .
Before starting the cold intervention, it should be medically clarified whether cold applications should be modified or are contraindicated for certain diseases, such as heart disease.
Tip: Take a cold shower every morning.
Nutrition, food supplements
- Probiotics such as Lactobacillus rhamnosus, which caused a reduction in stress hormones, depression and anxiety behaviour by means of the vagus nerve . Bifidobacterium longum was also able to reduce anxiety behaviour by means of the vagus nerve .
- Omega-3 fatty acids, especially rich in fatty fish , , , .
- Serotonin: Intestinal serotonin stimulates 5-HT3 receptors of vagal afferent fibres to stimulate vagal sensory neurons ..
- Choline: By increasing vagal activity, choline, e.g. contained in eggs, can improve cardiovascular damage .
- Zinc: Orally administered zinc increases food intake by vagal stimulation in rats during early-stage zinc deficiency (i.e. without decreasing plasma and tissue zinc concentrations) .
Tip: Make sure you get enough zinc in your diet.
Fasting - Fasting increases vagal activity : In animal experiments, intermittent fasting, as well as calorie-reduced food intake, led to a decrease in the low-frequency component of DPV spectra, a marker of sympathetic tone, and an increase in the high-frequency components of HRV spectra, a marker of parasympathetic activity .
Physical exercise - Light to moderate physical exercise seems to stimulate gastric emptying by increasing vagal activity .
Massage - For example, foot massage . Massage by means of vagal stimulation can also support weight gain in premature births , . Massage of the sinus carotids can even suppress epileptic seizures . This type of massage should only be performed by specialist therapists.
Sleeping position - Sleeping on the right side: In a study of the effect of lying positions on autonomic nerve modulation in patients with coronary artery disease, it was found that vagal activity was highest and sympathetic arousal lowest in the right lateral position. Vagal modulation in the supine position was significantly lowest of all sleep positions studied .
Electromagnetic fields - Exposure to pulsed electromagnetic fields for 20 minutes led to a faster recovery of heart rate variability, especially in the very low frequency range after physical exercise. After the magnetic field exposure was terminated, the described effects quickly subsided .
Glucagon-like peptide-1 secretion - GLP-1 inhibits gastric emptying via vagal afferent-mediated central mechanisms . Stimulation of endogenous GLP-1 secretion by manipulating dietary composition may be a relevant strategy for the treatment of obesity and type 2 diabetes. GLP-1 is mainly synthesised and secreted by enteroendocrine L-cells of the digestive tract. Its secretion is partly mediated by direct nutrient uptake through G-protein-coupled receptors. These bind to monosaccharides, peptides and amino acids, monounsaturated and polyunsaturated fatty acids, and short-chain fatty acids. High-fibre foods, nuts, avocados and eggs also appear to influence GLP-1 .
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- Lessons by Bruno Donatini at the OSD, Hamburg 2021