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Annals of the New York Academy of... Oct 2019With few effective treatments available, the global rise of metabolic diseases, including obesity, type 2 diabetes mellitus, and cardiovascular disease, seems... (Review)
Review
With few effective treatments available, the global rise of metabolic diseases, including obesity, type 2 diabetes mellitus, and cardiovascular disease, seems unstoppable. Likely caused by an obesogenic environment interacting with genetic susceptibility, the pathophysiology of obesity and metabolic diseases is highly complex and involves crosstalk between many organs and systems, including the brain. The vagus nerve is in a key position to bidirectionally link several peripheral metabolic organs with the brain and is increasingly targeted for neuromodulation therapy to treat metabolic disease. Here, we review the basics of vagal functional anatomy and its implications for vagal neuromodulation therapies. We find that most existing vagal neuromodulation techniques either ignore or misinterpret the rich functional specificity of both vagal efferents and afferents as demonstrated by a large body of literature. This lack of specificity of manipulating vagal fibers is likely the reason for the relatively poor beneficial long-term effects of such therapies. For these therapies to become more effective, rigorous validation of all physiological endpoints and optimization of stimulation parameters as well as electrode placements will be necessary. However, given the large number of function-specific fibers in any vagal branch, genetically guided neuromodulation techniques are more likely to succeed.
Topics: Animals; Electric Stimulation; Humans; Metabolic Diseases; Nerve Block; Obesity; Vagus Nerve
PubMed: 31268181
DOI: 10.1111/nyas.14182 -
European Journal of Pharmacology Aug 2023The vagus nerve is a major pathway in the body that is responsible for regulating the activity of the parasympathetic nervous system, which plays an important role in...
The vagus nerve is a major pathway in the body that is responsible for regulating the activity of the parasympathetic nervous system, which plays an important role in mood disorders including anxiety and depression. Fluoxetine, also known as Prozac, is widely used to treat depression. Nevertheless, there are few studies on the vagus nerve-mediated action of fluoxetine. In this study, we aimed to investigate the vagus nerve-dependent actions of fluoxetine in mice with restraint stress-induced or antibiotics-induced anxiety- and depression-like behaviors. Compared to sham operation, vagotomy alone did not exhibit significant effects on behavioral changes and serotonin-related biomarkers in mice not exposed to stress, antibiotics, or fluoxetine. Oral administration of fluoxetine significantly alleviated anxiety- and depression-like behaviors. However, celiac vagotomy significantly attenuated the anti-depressive effects of fluoxetine. The vagotomy also inhibited the effect of fluoxetine to attenuate restraint stress- or cefaclor-induced reduction in serotonin levels and Htr1a mRNA expression in the hippocampus. These findings suggest that the vagus nerve may regulate the efficacy of fluoxetine for depression.
Topics: Mice; Animals; Fluoxetine; Depression; Serotonin; Anxiety; Vagus Nerve; Hippocampus
PubMed: 37331682
DOI: 10.1016/j.ejphar.2023.175862 -
Acute Visceral Pain in Rats: Vagal Nerve Block Compared to Bupivacaine Administered Intramuscularly.Anesthesia and Analgesia Nov 2021Visceral and parietal peritoneum layers have different sensory innervations. Most visceral peritoneum sensory information is conveyed via the vagus nerve to the nucleus... (Comparative Study)
Comparative Study
BACKGROUND
Visceral and parietal peritoneum layers have different sensory innervations. Most visceral peritoneum sensory information is conveyed via the vagus nerve to the nucleus of the solitary tract (NTS). We already showed in animal models that intramuscular (i.m.) injection of local anesthetics decreases acute somatic and visceral pain and general inflammation induced by aseptic peritonitis. The goal of the study was to compare the effects of parietal block, i.m. bupivacaine, and vagotomy on spinal cord and NTS stimulation induced by a chemical peritonitis.
METHODS
We induced peritonitis in rats using carrageenan and measured cellular activation in spinal cord and NTS under the following conditions, that is, a parietal nerve block with bupivacaine, a chemical right vagotomy, and i.m. microspheres loaded with bupivacaine. Proto-oncogene c-Fos (c-Fos), cluster of differentiation protein 11b (CD11b), and tumor necrosis factor alpha (TNF-α) expression in cord and NTS were studied.
RESULTS
c-Fos activation in the cord was inhibited by nerve block 2 hours after peritoneal insult. Vagotomy and i.m. bupivacaine similarly inhibited c-Fos activation in NTS. Forty-eight hours after peritoneal insult, the number of cells expressing CD11b significantly increased in the cord (P = .010). The median difference in the effect of peritonitis compared to control was 30 cells (CI95, 13.5-55). TNF-α colocalized with CD11b. Vagotomy inhibited this microglial activation in the NTS, but not in the cord. This activation was inhibited by i.m. bupivacaine both in cord and in NTS. The median difference in the effect of i.m. bupivacaine added to peritonitis was 29 cells (80% increase) in the cord and 18 cells (75% increase) in the NTS. Our study underlines the role of the vagus nerve in the transmission of an acute visceral pain message and confirmed that systemic bupivacaine prevents noxious stimuli by inhibiting c-Fos and microglia activation.
CONCLUSIONS
In rats receiving intraperitoneal carrageenan, i.m. bupivacaine similarly inhibited c-Fos and microglial activation both in cord and in the NTS. Vagal block inhibited activation only in the NTS. Our study underlines the role of the vagus nerve in the transmission of an acute visceral pain message and confirmed that systemic bupivacaine prevents noxious stimuli. This emphasizes the effects of systemic local anesthetics on inflammation and visceral pain.
Topics: Acute Pain; Anesthetics, Local; Animals; Bupivacaine; CD11b Antigen; Carrageenan; Disease Models, Animal; Injections, Intramuscular; Male; Microglia; Pain Management; Peritonitis; Proto-Oncogene Proteins c-fos; Rats, Sprague-Dawley; Solitary Nucleus; Spinal Cord; Tumor Necrosis Factor-alpha; Vagotomy; Vagus Nerve; Visceral Pain; Rats
PubMed: 34347648
DOI: 10.1213/ANE.0000000000005697 -
Animals : An Open Access Journal From... Sep 2022The aim was to investigate the potential effect of adropin (ADR) on pancreatic−biliary juice (PBJ) secretion (volume, protein content, trypsin activity) in a rat...
The aim was to investigate the potential effect of adropin (ADR) on pancreatic−biliary juice (PBJ) secretion (volume, protein content, trypsin activity) in a rat model. The animals were divided into control and five experimental groups: adropin, CCK-8 (CCK-8 stimulation), capsaicin (capsaicin deactivation of afferents), vagotomy (vagotomy procedure), and vagal stimulation (vagal nerve stimulation). The experiment consisted of four phases, during which vehicle (0.9% NaCl) and three ADR boluses (5, 10, and 20 µg/kg BW) were administered i.v. every 30 min. PBJ samples were collected from each rat at 15 min intervals after boluses. Exogenous ADR failed to affect the pancreatic responses after vagotomy and the capsaicin pretreatment and reduced the PBJ volume, protein outputs, and trypsin activity in the adropin, CCK-8, and vagal stimulation groups in a dose-dependent manner. In all these groups, volume of PBJ was reduced only by the highest dose of ADR (p < 0.001 for adropin group and p < 0.01 for CCK-8 and vagal stimulation groups), and the protein outputs were reduced by the administration of ADR 10 µg/kg BW (adropin and CCK-8 groups, p < 0.01 in both cases) and 20 µg/kg BW (p < 0.001 for adropin and CCK-8 groups, p < 0.01 for vagal stimulation group). The 10 µg/kg BW dose of ADR reduced the trypsin output in the CCK-8 group (p < 0.01), and the highest ADR dose reduced the trypsin output in the CCK-8 (p < 0.001) and vagal stimulation (p < 0.01) groups. In conclusion, adropin in the analyzed doses exhibits the negative feedback pathway. This mechanism seems to participate in the regulation of pancreatic juice secretion via an indirect vagal mechanism.
PubMed: 36230288
DOI: 10.3390/ani12192547 -
Progress in Brain Research 2023Neuroinflammation plays a key role in the pathogenesis of major depressive disorder (MDD), including treatment-resistant depression (TRD). Patients with TRD have higher...
Neuroinflammation plays a key role in the pathogenesis of major depressive disorder (MDD), including treatment-resistant depression (TRD). Patients with TRD have higher levels of inflammatory biomarkers compared with responders to antidepressants. Multiple lines of evidence suggest that the gut-microbiota-brain axis via the vagus nerve plays a key role in neuroinflammation. Preclinical and clinical data suggest that fecal microbiota transplantation (FMT) from MDD patients or rodents with depression-like behaviors cause depression-like behaviors in rodents through systemic inflammation. Importantly, subdiaphragmatic vagotomy blocked these depression-like phenotypes and systemic inflammation in rodents after FMT of depression-related microbes. Subdiaphragmatic vagotomy also blocked the antidepressant-like effects of serotonergic antidepressants in rodents. Preclinical findings suggest that the new antidepressant, (R)-ketamine (or arketamine), may restore the altered composition of gut microbiota in rodents with depression-like behaviors, contributing to the beneficial effects of arketamine. In this chapter, the author reviews the role of the vagus nerve-dependent gut-microbiota-brain axis in depression (including TRD), and also discuss the potential of FMT, vagus nerve stimulation, and arketamine for the treatment of TRD.
Topics: Humans; Depression; Depressive Disorder, Major; Neuroinflammatory Diseases; Microbiota; Antidepressive Agents; Inflammation; Vagus Nerve; Brain
PubMed: 37414494
DOI: 10.1016/bs.pbr.2023.01.003 -
Journal of Inflammation Research 2023Current pharmacological approaches to prevent hepatic ischemia/reperfusion injury (IRI) are limited. To mitigate hepatic injury, more research is needed to improve the...
Electroacupuncture Pretreatment at Zusanli (ST36) Ameliorates Hepatic Ischemia/Reperfusion Injury in Mice by Reducing Oxidative Stress via Activating Vagus Nerve-Dependent Nrf2 Pathway.
BACKGROUND AND PURPOSE
Current pharmacological approaches to prevent hepatic ischemia/reperfusion injury (IRI) are limited. To mitigate hepatic injury, more research is needed to improve the understanding of hepatic IRI. Depending on traditional Chinese medicine (TCM) theory, acupuncture therapy has been used for the treatment of ischemic diseases with good efficacy. However, the efficacy and mechanism of acupuncture for hepatic IRI are still unclear.
METHODS
Blood provided to the left and middle lobe of mice livers was blocked with a non-invasive clamp and then the clamps were removed for reperfusion to establish a liver IRI model. Quantitative proteomics approach was used to evaluate the impact of EA pretreatment on liver tissue proteome in the IRI group. Serum biochemistry was used to detect liver injury, inflammation, and oxidative stress levels. H&E staining and TUNEL staining were used to detect hepatocyte injury and apoptosis. Immunohistochemistry and ELISA were used to detect the degree of inflammatory cell infiltration and the level of inflammation. The anti-inflammatory and antioxidant capacities were detected by Quantitative RT-PCR and Western blotting.
RESULTS
We found that EA at Zusanli (ST36) has a protective effect on hepatic IRI in mice by alleviating oxidative stress, hepatocyte death, and inflammation response. Nuclear factor E2-related factor 2 (Nrf2) as a crucial target was regulated by EA and was then successfully validated. The Nrf2 inhibitor ML385 and cervical vagotomy eliminated the protective effect in the EA treatment group.
CONCLUSION
This study firstly demonstrated that EA pretreatment at ST36 significantly ameliorates hepatic IRI in mice by inhibiting oxidative stress via activating the Nrf2 signal pathway, which was vagus nerve-dependent.
PubMed: 37092126
DOI: 10.2147/JIR.S404087 -
American Journal of Physiology.... Jun 2021The nucleus tractus solitarii (nTS) is the initial site of integration of sensory information from the cardiorespiratory system and contributes to reflex responses to...
The nucleus tractus solitarii (nTS) is the initial site of integration of sensory information from the cardiorespiratory system and contributes to reflex responses to hypoxia. Afferent fibers of the bilateral vagus nerves carry input from the heart, lungs, and other organs to the nTS where it is processed and modulated. Vagal afferents and nTS neurons are integrally associated with astrocytes and microglia that contribute to neuronal activity and influence cardiorespiratory control. We hypothesized that vagotomy would alter glial morphology and cardiorespiratory responses to hypoxia. Unilateral vagotomy (or sham surgery) was performed in rats. Prior to and seven days after surgery, baseline and hypoxic cardiorespiratory responses were monitored in conscious and anesthetized animals. The brainstem was sectioned and caudal, mid-area postrema (mid-AP), and rostral sections of the nTS were prepared for immunohistochemistry. Vagotomy increased immunoreactivity (-IR) of astrocytic glial fibrillary acidic protein (GFAP), specifically at mid-AP in the nTS. Similar results were found in the dorsal motor nucleus of the vagus (DMX). Vagotomy did not alter nTS astrocyte number, yet increased astrocyte branching and altered morphology. In addition, vagotomy both increased nTS microglia number and produced morphologic changes indicative of activation. Cardiorespiratory baseline parameters and hypoxic responses remained largely unchanged, but vagotomized animals displayed fewer augmented breaths (sighs) in response to hypoxia. Altogether, vagotomy alters nTS glial morphology, indicative of functional changes in astrocytes and microglia that may affect cardiorespiratory function in health and disease.
Topics: Animals; Astrocytes; Hypoxia; Male; Microglia; Neuroglia; Neurons; Rats, Sprague-Dawley; Solitary Nucleus; Vagotomy; Vagus Nerve; Rats
PubMed: 33978480
DOI: 10.1152/ajpregu.00019.2021 -
Science Advances Jul 2023The blood circulation is considered the only way for the orally administered nanoparticles to enter the central nervous systems (CNS), whereas non-blood route-mediated...
The blood circulation is considered the only way for the orally administered nanoparticles to enter the central nervous systems (CNS), whereas non-blood route-mediated nanoparticle translocation between organs is poorly understood. Here, we show that peripheral nerve fibers act as direct conduits for silver nanomaterials (Ag NMs) translocation from the gut to the CNS in both mice and rhesus monkeys. After oral gavage, Ag NMs are significantly enriched in the brain and spinal cord of mice with particle state however do not efficiently enter the blood. Using truncal vagotomy and selective posterior rhizotomy, we unravel that the vagus and spinal nerves mediate the transneuronal translocation of Ag NMs from the gut to the brain and spinal cord, respectively. Single-cell mass cytometry analysis revealed that enterocytes and enteric nerve cells take up significant levels of Ag NMs for subsequent transfer to the connected peripheral nerves. Our findings demonstrate nanoparticle transfer along a previously undocumented gut-CNS axis mediated by peripheral nerves.
Topics: Animals; Mice; Silver; Central Nervous System; Spinal Cord; Peripheral Nerves; Nanostructures
PubMed: 37418525
DOI: 10.1126/sciadv.adg2252 -
Bioengineering (Basel, Switzerland) Jul 2023A code is generally defined as a system of signals or symbols for communication. Experimental evidence is synthesized for the presence and utility of such communication... (Review)
Review
A code is generally defined as a system of signals or symbols for communication. Experimental evidence is synthesized for the presence and utility of such communication in heart rate variability (HRV) with particular attention to fetal HRV: HRV contains signatures of information flow between the organs and of response to physiological or pathophysiological stimuli as signatures of states (or syndromes). HRV exhibits features of time structure, phase space structure, specificity with respect to (organ) target and pathophysiological syndromes, and universality with respect to species independence. Together, these features form a spatiotemporal structure, a phase space, that can be conceived of as a manifold of a yet-to-be-fully understood dynamic complexity. The objective of this article is to synthesize physiological evidence supporting the existence of HRV code: hereby, the process-specific subsets of HRV measures indirectly map the phase space traversal reflecting the specific information contained in the code required for the body to regulate the physiological responses to those processes. The following physiological examples of HRV code are reviewed, which are reflected in specific changes to HRV properties across the signal-analytical domains and across physiological states and conditions: the fetal systemic inflammatory response, organ-specific inflammatory responses (brain and gut), chronic hypoxia and intrinsic (heart) HRV (iHRV), allostatic load (physiological stress due to surgery), and vagotomy (bilateral cervical denervation). Future studies are proposed to test these observations in more depth, and the author refers the interested reader to the referenced publications for a detailed study of the HRV measures involved. While being exemplified mostly in the studies of fetal HRV, the presented framework promises more specific fetal, postnatal, and adult HRV biomarkers of health and disease, which can be obtained non-invasively and continuously.
PubMed: 37508849
DOI: 10.3390/bioengineering10070822 -
Alimentary Pharmacology & Therapeutics Jun 2020The vagus nerve provides essential parasympathetic innervation to the gastrointestinal system and is known to have anti-inflammatory properties.
BACKGROUND
The vagus nerve provides essential parasympathetic innervation to the gastrointestinal system and is known to have anti-inflammatory properties.
AIMS
To explore the relationship between vagotomy and the risk of inflammatory bowel disease (IBD) and its major categories: Crohn's disease (CD) and ulcerative colitis (UC).
METHODS
A matched cohort comprising 15 637 patients undergoing vagotomy was identified through the Swedish Patient Register from 1964 to 2010. Each vagotomised patient was matched for birth year and gender with 40 nonvagotomised individuals on the date of vagotomy. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for IBD using flexible parametric models adjusted for matching variables, year of vagotomy, birth country, chronic obstructive pulmonary disease and comorbidity index.
RESULTS
We observed 119 (0.8%) patients with vagotomy developed IBD compared to 3377 (0.5%) IBD cases in nonvagotomised individuals. The crude incidence of IBD (per 1000 person-years) was 0.38 for vagotomised patients and 0.25 for nonvagotomised individuals. We observed a time-dependent elevated risk of IBD associated with vagotomy, for instance, the HR (95% CI) was 1.80 (1.40-2.31) at year 5 and 1.49 (1.14-1.96) at year 10 post-vagotomy. The association appeared to be stronger for truncal than selective vagotomy and limited to CD (HR was 3.63 [1.94-6.80] for truncal and 2.06 [1.49-2.84] for selective vagotomy) but not UC (1.36 [0.71-2.62] for truncal and 1.25 [0.95-1.63] for selective vagotomy).
CONCLUSIONS
We found a positive association between vagotomy and later IBD, particularly for CD. The finding indirectly underlines the beneficial role of the vagal tone in IBD.
Topics: Adult; Aged; Aged, 80 and over; Case-Control Studies; Cohort Studies; Colitis, Ulcerative; Crohn Disease; Female; Humans; Incidence; Inflammatory Bowel Diseases; Male; Middle Aged; Postoperative Complications; Registries; Risk Factors; Sweden; Vagotomy
PubMed: 32319125
DOI: 10.1111/apt.15715