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Chang X, Zhang H, Chen S. Neural circuits regulating visceral pain. Commun Biol 2024; 7:457. [PMID: 38615103 PMCID: PMC11016080 DOI: 10.1038/s42003-024-06148-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 04/05/2024] [Indexed: 04/15/2024] Open
Abstract
Visceral hypersensitivity, a common clinical manifestation of irritable bowel syndrome, may contribute to the development of chronic visceral pain, which is a major challenge for both patients and health providers. Neural circuits in the brain encode, store, and transfer pain information across brain regions. In this review, we focus on the anterior cingulate cortex and paraventricular nucleus of the hypothalamus to highlight the progress in identifying the neural circuits involved in visceral pain. We also discuss several neural circuit mechanisms and emphasize the importance of cross-species, multiangle approaches and the identification of specific neurons in determining the neural circuits that control visceral pain.
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Affiliation(s)
- Xiaoli Chang
- College of Acupuncture and Massage, Shandong University of Traditional Chinese Medicine, Jinan, 250355, China.
- Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, 250355, China.
| | - Haiyan Zhang
- Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, 250355, China
| | - Shaozong Chen
- Research Institute of Acupuncture and Moxibustion, Shandong University of Traditional Chinese Medicine, Jinan, 250355, China.
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Wang RL, Chang RB. The Coding Logic of Interoception. Annu Rev Physiol 2024; 86:301-327. [PMID: 38061018 PMCID: PMC11103614 DOI: 10.1146/annurev-physiol-042222-023455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/13/2024]
Abstract
Interoception, the ability to precisely and timely sense internal body signals, is critical for life. The interoceptive system monitors a large variety of mechanical, chemical, hormonal, and pathological cues using specialized organ cells, organ innervating neurons, and brain sensory neurons. It is important for maintaining body homeostasis, providing motivational drives, and regulating autonomic, cognitive, and behavioral functions. However, compared to external sensory systems, our knowledge about how diverse body signals are coded at a system level is quite limited. In this review, we focus on the unique features of interoceptive signals and the organization of the interoceptive system, with the goal of better understanding the coding logic of interoception.
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Affiliation(s)
- Ruiqi L Wang
- Department of Neuroscience and Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA;
| | - Rui B Chang
- Department of Neuroscience and Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, USA;
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Zhang Y, Huang W, Shan Z, Zhou Y, Qiu T, Hu L, Yang L, Wang Y, Xiao Z. A new experimental rat model of nocebo-related nausea involving double mechanisms of observational learning and conditioning. CNS Neurosci Ther 2024; 30:e14389. [PMID: 37545429 PMCID: PMC10848046 DOI: 10.1111/cns.14389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 07/12/2023] [Accepted: 07/23/2023] [Indexed: 08/08/2023] Open
Abstract
AIM The nocebo effect, such as nausea and vomiting, is one of the major reasons patients discontinue therapy. The underlying mechanisms remain unknown due to a lack of reliable experimental models. The goal of this study was to develop a new animal model of nocebo-related nausea by combining observational learning and Pavlovian conditioning paradigms. METHODS Male Sprague-Dawley rats with nitroglycerin-induced migraine were given 0.9% saline (a placebo) or LiCl (a nausea inducer) following headache relief, according to different paradigms. RESULTS Both strategies provoked nocebo nausea responses, with the conditioning paradigm having a greater induction impact. The superposition of two mechanisms led to a further increase in nausea responses. A preliminary investigation of the underlying mechanism revealed clearly raised peripheral and central cholecystokinin (CCK) levels, as well as specific changes in the 5-hydroxytryptamine and cannabinoid systems. Brain networks related to emotion, cognition, and visceral sense expressed higher c-Fos-positive neurons, including the anterior cingulate cortex (ACC), insula, basolateral amygdala (BLA), thalamic paraventricular nucleus (PVT), hypothalamic paraventricular nucleus (PVN), nucleus tractus solitarius (NTS), periaqueductal gray (PAG), and dorsal raphe nucleus-dorsal part (DRD). We also found that nausea expectances in the model could last for at least 12 days. CONCLUSION The present study provides a useful experimental model of nocebo nausea that might be used to develop potential molecular pathways and therapeutic strategies for nocebo.
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Affiliation(s)
- Yu Zhang
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
- Central LaboratoryRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Wanbin Huang
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
- Central LaboratoryRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Zhengming Shan
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
- Central LaboratoryRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Yanjie Zhou
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
- Central LaboratoryRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Tao Qiu
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Luyu Hu
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Liu Yang
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Yue Wang
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
| | - Zheman Xiao
- Department of NeurologyRenmin Hospital of Wuhan UniversityWuhanHubei ProvinceChina
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Naviaux RK. Mitochondrial and metabolic features of salugenesis and the healing cycle. Mitochondrion 2023; 70:131-163. [PMID: 37120082 DOI: 10.1016/j.mito.2023.04.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 03/24/2023] [Accepted: 04/23/2023] [Indexed: 05/01/2023]
Abstract
Pathogenesis and salugenesis are the first and second stages of the two-stage problem of disease production and health recovery. Salugenesis is the automatic, evolutionarily conserved, ontogenetic sequence of molecular, cellular, organ system, and behavioral changes that is used by living systems to heal. It is a whole-body process that begins with mitochondria and the cell. The stages of salugenesis define a circle that is energy- and resource-consuming, genetically programmed, and environmentally responsive. Energy and metabolic resources are provided by mitochondrial and metabolic transformations that drive the cell danger response (CDR) and create the three phases of the healing cycle: Phase 1-Inflammation, Phase 2-Proliferation, and Phase 3-Differentiation. Each phase requires a different mitochondrial phenotype. Without different mitochondria there can be no healing. The rise and fall of extracellular ATP (eATP) signaling is a key driver of the mitochondrial and metabolic reprogramming required to progress through the healing cycle. Sphingolipid and cholesterol-enriched membrane lipid rafts act as rheostats for tuning cellular sensitivity to purinergic signaling. Abnormal persistence of any phase of the CDR inhibits the healing cycle, creates dysfunctional cellular mosaics, causes the symptoms of chronic disease, and accelerates the process of aging. New research reframes the rising tide of chronic disease around the world as a systems problem caused by the combined action of pathogenic triggers and anthropogenic factors that interfere with the mitochondrial functions needed for healing. Once chronic pain, disability, or disease is established, salugenesis-based therapies will start where pathogenesis-based therapies end.
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Affiliation(s)
- Robert K Naviaux
- The Mitochondrial and Metabolic Disease Center, Departments of Medicine, and Pediatrics, University of California, San Diego School of Medicine, 214 Dickinson St., Bldg CTF, Rm C107, MC#8467, San Diego, CA 92103.
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Sharvin BL, Aburto MR, Cryan JF. Decoding the neurocircuitry of gut feelings: Region-specific microbiome-mediated brain alterations. Neurobiol Dis 2023; 179:106033. [PMID: 36758820 DOI: 10.1016/j.nbd.2023.106033] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 01/31/2023] [Accepted: 02/02/2023] [Indexed: 02/10/2023] Open
Abstract
Research in the last decade has unveiled a crucial role for the trillions of microorganisms that reside in the gut in influencing host neurodevelopment across the lifespan via the microbiota-gut-brain axis. Studies have linked alterations in the composition, complexity, and diversity of the gut microbiota to changes in behaviour including abnormal social interactions, cognitive deficits, and anxiety- and depressive-like phenotypes. Moreover, the microbiota has been linked with neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. Interestingly, there appears to be specific brain regions governing the neurocircuitry driving higher cognitive function that are susceptible to influence from manipulations to the host microbiome. This review will aim to elucidate the region-specific effects mediated by the gut microbiota, with a focus on translational animal models and some existing human neuroimaging data. Compelling preclinical evidence suggests disruption to normal microbiota-gut-brain signalling can have detrimental effects on the prefrontal cortex, amygdala, hippocampus, hypothalamus, and striatum. Furthermore, human neuroimaging studies have unveiled a role for the microbiota in mediating functional connectivity and structure of specific brain regions that can be traced back to neurocognition and behavioural output. Understanding these microbiota-mediated changes will aid in identifying unique therapeutic targets for treating neurological disorders associated with these regions.
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Affiliation(s)
- Brendan L Sharvin
- APC Microbiome, University College Cork, Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - Maria Rodriguez Aburto
- APC Microbiome, University College Cork, Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland
| | - John F Cryan
- APC Microbiome, University College Cork, Cork, Ireland; Department of Anatomy and Neuroscience, University College Cork, Cork, Ireland.
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Clyburn C, Li MH, Ingram SL, Andresen MC, Habecker BA. Cholinergic collaterals arising from noradrenergic sympathetic neurons in mice. J Physiol 2023; 601:1247-1264. [PMID: 36797985 PMCID: PMC10065914 DOI: 10.1113/jp284059] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 02/07/2023] [Indexed: 02/18/2023] Open
Abstract
The sympathetic nervous system vitally regulates autonomic functions, including cardiac activity. Postganglionic neurons of the sympathetic chain ganglia relay signals from the central nervous system to autonomic peripheral targets. Disrupting this flow of information often dysregulates organ function and leads to poor health outcomes. Despite the importance of these sympathetic neurons, fundamental aspects of the neurocircuitry within peripheral ganglia remain poorly understood. Conventionally, simple monosynaptic cholinergic pathways from preganglionic neurons are thought to activate postganglionic sympathetic neurons. However, early studies suggested more complex neurocircuits may be present within sympathetic ganglia. The present study recorded synaptic responses in sympathetic stellate ganglia neurons following electrical activation of the pre- and postganglionic nerve trunks and used genetic strategies to assess the presence of collateral projections between postganglionic neurons of the stellate ganglia. Orthograde activation of the preganglionic nerve trunk, T-2, uncovered high jitter synaptic latencies consistent with polysynaptic connections. Pharmacological inhibition of nicotinic acetylcholine receptors with hexamethonium blocked all synaptic events. To confirm that high jitter, polysynaptic events were due to the presence of cholinergic collaterals from postganglionic neurons within the stellate ganglion, we knocked out choline acetyltransferase in adult noradrenergic neurons. This genetic knockout eliminated orthograde high jitter synaptic events and EPSCs evoked by retrograde activation. These findings suggest that cholinergic collateral projections arise from noradrenergic neurons within sympathetic ganglia. Identifying the contributions of collateral excitation to normal physiology and pathophysiology is an important area of future study and may offer novel therapeutic targets for the treatment of autonomic imbalance. KEY POINTS: Electrical stimulation of a preganglionic nerve trunk evoked fast synaptic transmission in stellate ganglion neurons with low and high jitter latencies. Retrograde stimulation of a postganglionic nerve trunk evoked direct, all-or-none action currents and delayed nicotinic EPSCs indistinguishable from orthogradely-evoked EPSCs in stellate neurons. Nicotinic acetylcholine receptor blockade prevented all spontaneous and evoked synaptic activity. Knockout of acetylcholine production in noradrenergic neurons eliminated all retrogradely-evoked EPSCs but did not change retrograde action currents, indicating that noradrenergic neurons have cholinergic collaterals connecting neurons within the stellate ganglion.
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Affiliation(s)
- Courtney Clyburn
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Ming-Hua Li
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Susan L Ingram
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, USA
| | - Michael C Andresen
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
| | - Beth A Habecker
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, USA
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Mota CMD, Madden CJ. Neural control of the spleen as an effector of immune responses to inflammation: mechanisms and treatments. Am J Physiol Regul Integr Comp Physiol 2022; 323:R375-R384. [PMID: 35993560 PMCID: PMC9485006 DOI: 10.1152/ajpregu.00151.2022] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/29/2022] [Accepted: 08/11/2022] [Indexed: 11/22/2022]
Abstract
Immune system responses are a vital defense mechanism against pathogens. Inflammatory mediators finely regulate complex inflammatory responses from initiation to resolution. However, in certain conditions, the inflammation is initiated and amplified, but not resolved. Understanding the biological mechanisms underlying the regulation of the immune response is critical for developing therapeutic alternatives, including pharmaceuticals and bioelectronic tools. The spleen is an important immune effector organ since it orchestrates innate and adaptive immune responses such as pathogen clearance, cytokine production, and differentiation of cells, therefore playing a modulatory role that balances pro- and anti-inflammatory responses. However, modulation of splenic immune activity is a largely unexplored potential therapeutic tool that could be used for the treatment of inflammatory and life-threatening conditions. This review discusses some of the mechanisms controlling neuroimmune communication and the brain-spleen axis.
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Affiliation(s)
- Clarissa M D Mota
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon
| | - Christopher J Madden
- Department of Neurological Surgery, Oregon Health and Science University, Portland, Oregon
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Ottaviani MM, Macefield VG. Structure and Functions of the Vagus Nerve in Mammals. Compr Physiol 2022; 12:3989-4037. [PMID: 35950655 DOI: 10.1002/cphy.c210042] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We review the structure and function of the vagus nerve, drawing on information obtained in humans and experimental animals. The vagus nerve is the largest and longest cranial nerve, supplying structures in the neck, thorax, and abdomen. It is also the only cranial nerve in which the vast majority of its innervation territory resides outside the head. While belonging to the parasympathetic division of the autonomic nervous system, the nerve is primarily sensory-it is dominated by sensory axons. We discuss the macroscopic and microscopic features of the nerve, including a detailed description of its extensive territory. Histochemical and genetic profiles of afferent and efferent axons are also detailed, as are the central nuclei involved in the processing of sensory information conveyed by the vagus nerve and the generation of motor (including parasympathetic) outflow via the vagus nerve. We provide a comprehensive review of the physiological roles of vagal sensory and motor neurons in control of the cardiovascular, respiratory, and gastrointestinal systems, and finish with a discussion on the interactions between the vagus nerve and the immune system. © 2022 American Physiological Society. Compr Physiol 12: 1-49, 2022.
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Affiliation(s)
- Matteo M Ottaviani
- Department of Neurosurgery, Università Politecnica delle Marche, Ancona, Italy
| | - Vaughan G Macefield
- Baker Heart and Diabetes Institute, Melbourne, Australia.,Baker Department of Cardiometabolic Health, University of Melbourne, Melbourne, Australia.,Department of Anatomy & Physiology, University of Melbourne, Melbourne, Australia
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Tjen-A-Looi SC, Fu LW, Guo ZL, Gong YD, Nguyen ATN, Nguyen ATP, Malik S. Neurogenic Hypotension and Bradycardia Modulated by Electroacupuncture in Hypothalamic Paraventricular Nucleus. Front Neurosci 2022; 16:934752. [PMID: 35958987 PMCID: PMC9361000 DOI: 10.3389/fnins.2022.934752] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 06/23/2022] [Indexed: 11/13/2022] Open
Abstract
Electroacupuncture (EA) stimulates somatic median afferents underlying P5-6 acupoints and modulates parasympathoexcitatory reflex responses through central processing in the brainstem. Although decreases in blood pressure and heart rate by the neural-mediated Bezold-Jarisch reflex responses are modulated by EA through opioid actions in the nucleus tractus solitarius and nucleus ambiguus, the role of the hypothalamus is unclear. The hypothalamic paraventricular nucleus (PVN) is activated by sympathetic afferents and regulates sympathetic outflow and sympathoexcitatory cardiovascular responses. In addition, the PVN is activated by vagal afferents, but little is known about its regulation of cardiopulmonary inhibitory hemodynamic responses. We hypothesized that the PVN participates in the Bezold-Jarisch reflex responses and EA inhibits these cardiopulmonary responses through the PVN opioid system. Rats were anesthetized and ventilated, and their heart rate and blood pressures were monitored. Application of phenylbiguanide every 10 min close to the right atrium induced consistent depressor and bradycardia reflex responses. Unilateral microinjection of the depolarization blockade agent kainic acid or glutamate receptor antagonist kynurenic acid in the PVN reduced these reflex responses. In at least 70% of the rats, 30 min of bilateral EA at P5-6 acupoints reduced the depressor and bradycardia responses for at least 60 min. Blockade of the CCK-1 receptors converted the non-responders into EA-responders. Unilateral PVN-microinjection with naloxone reversed the EA inhibition. Vagal-evoked activity of the PVN cardiovascular neurons was reduced by 30 min EA (P5-6) through opioid receptor activation. These data indicate that PVN processes inhibitory cardiopulmonary reflexes and participates in EA-modulation of the neural-mediated vasodepression and bradycardia.
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Non-invasive vagus nerve stimulation modulates trigeminal but not somatosensory perception: functional evidence for a trigemino-vagal system in humans. Pain 2022; 163:1978-1986. [PMID: 35082253 DOI: 10.1097/j.pain.0000000000002595] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Accepted: 01/07/2022] [Indexed: 11/26/2022]
Abstract
ABSTRACT Non-invasive vagus nerve stimulation (nVNS) is effective in several types of headache disorders. We sought to unravel the mechanism of how nVNS exhibits this efficacy. This study used a randomized, single-blind, sham-controlled, crossover-design, and comprised three projects with three independent cohorts of healthy participants. Project I (n=15) was explorative. Six quantitative sensory test (QST) parameters, including mechanical pain threshold (MPT), were measured over the left V1 dermatome and forearm, and compared before and after unilateral nVNS. Projects II (n=20) and III (n=21) were online pre-registered . QST parameters were compared over the left (Project II) or bilateral V1 and V3 dermatomes (Project III), respectively, in addition to the left forearm as a control. A secondary analysis of heart rate variability (HRV) using a historical control group was used to control for systemic effects of nVNS. Verum-nVNS induced trigeminal-specific modulation of pain threshold (i.e., MPT) over the left V1 in Project I, left V1 and V3 in Project II, and bilateral V1 and V3 in Project III. Data pooled from Project II and III demonstrated greater increase of MPT in the V1 vs. V3 dermatome. There were no differences associated with sham-nVNS in any projects. HRV parameters did not change after nVNS. Our results provide functional evidence of a long hypothesized functional trigemino-vagal system in humans and may explain why nVNS is effective in some headache but not in somatic pain disorders. Since unilateral nVNS modulated the trigeminal thresholds bilaterally, this effect is probably indirect through a central top-down mechanism.
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Cooper CM, Farrand AQ, Andresen MC, Beaumont E. Vagus nerve stimulation activates nucleus of solitary tract neurons via supramedullary pathways. J Physiol 2021; 599:5261-5279. [PMID: 34676533 DOI: 10.1113/jp282064] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 10/12/2021] [Indexed: 01/20/2023] Open
Abstract
Vagus nerve stimulation (VNS) treats patients with drug-resistant epilepsy, depression and heart failure, but the mechanisms responsible are uncertain. The mild stimulus intensities used in chronic VNS suggest activation of myelinated primary visceral afferents projecting to the nucleus of the solitary tract (NTS). Here, we monitored the activity of second and higher order NTS neurons in response to peripheral vagal activation using therapeutic VNS criteria. A bipolar stimulating electrode activated the left cervical vagus nerve, and stereotaxically placed single tungsten electrodes recorded unit activity from the left caudomedial NTS of chloralose-anaesthetized rats. High-intensity single electrical stimuli established vagal afferent conduction velocity (myelinated A-type or unmyelinated C-type) as well as synaptic order (second vs. higher order using paired electrical stimuli) for inputs to single NTS neurons. Then, VNS treatment was applied. A mid-collicular knife cut (KC) divided the brainstem from all supramedullary regions to determine their contribution to NTS activity. Our chief findings indicate that the KC reduced basal spontaneous activity of second-order NTS neurons receiving myelinated vagal input by 85%. In these neurons, acute VNS increased activity similarly in Control and KC animals. Interestingly, the KC interrupted VNS activation of higher order NTS neurons and second-order NTS neurons receiving unmyelinated vagal input, indicating that supramedullary descending projections to NTS are needed to amplify the peripheral neuronal signal from VNS. The present study begins to define the pathways activated during VNS and will help to better identify the central nervous system contributions to the therapeutic benefits of VNS therapy. KEY POINTS: Vagus nerve stimulation is routinely used in the clinic to treat epilepsy and depression, despite our uncertainty about how this treatment works. For this study, the connections between the nucleus of the solitary tract (NTS) and the higher brain regions were severed to learn more about their contribution to activity of these neurons during stimulation. Severing these brain connections reduced baseline activity as well as reducing stimulation-induced activation for NTS neurons receiving myelinated vagal input. Higher brain regions play a significant role in maintaining both normal activity in NTS and indirect mechanisms of enhancing NTS neuronal activity during vagus nerve stimulation.
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Affiliation(s)
- Coty M Cooper
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA
| | - Ariana Q Farrand
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA
| | | | - Eric Beaumont
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA
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