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Nature Nov 2023Visceral sensory pathways mediate homeostatic reflexes, the dysfunction of which leads to many neurological disorders. The Bezold-Jarisch reflex (BJR), first described...
Visceral sensory pathways mediate homeostatic reflexes, the dysfunction of which leads to many neurological disorders. The Bezold-Jarisch reflex (BJR), first described in 1867, is a cardioinhibitory reflex that is speculated to be mediated by vagal sensory neurons (VSNs) that also triggers syncope. However, the molecular identity, anatomical organization, physiological characteristics and behavioural influence of cardiac VSNs remain mostly unknown. Here we leveraged single-cell RNA-sequencing data and HYBRiD tissue clearing to show that VSNs that express neuropeptide Y receptor Y2 (NPY2R) predominately connect the heart ventricular wall to the area postrema. Optogenetic activation of NPY2R VSNs elicits the classic triad of BJR responses-hypotension, bradycardia and suppressed respiration-and causes an animal to faint. Photostimulation during high-resolution echocardiography and laser Doppler flowmetry with behavioural observation revealed a range of phenotypes reflected in clinical syncope, including reduced cardiac output, cerebral hypoperfusion, pupil dilation and eye-roll. Large-scale Neuropixels brain recordings and machine-learning-based modelling showed that this manipulation causes the suppression of activity across a large distributed neuronal population that is not explained by changes in spontaneous behavioural movements. Additionally, bidirectional manipulation of the periventricular zone had a push-pull effect, with inhibition leading to longer syncope periods and activation inducing arousal. Finally, ablating NPY2R VSNs specifically abolished the BJR. Combined, these results demonstrate a genetically defined cardiac reflex that recapitulates characteristics of human syncope at physiological, behavioural and neural network levels.
Topics: Humans; Area Postrema; Bradycardia; Cardiac Output, Low; Echocardiography; Heart; Heart Rate; Hypotension; Laser-Doppler Flowmetry; Nerve Net; Reflex; Sensory Receptor Cells; Single-Cell Gene Expression Analysis; Syncope; Vagus Nerve
PubMed: 37914931
DOI: 10.1038/s41586-023-06680-7 -
American Journal of Physiology. Heart... Oct 2023The cardiovascular response to exercise is largely determined by neurocirculatory control mechanisms that help to raise blood pressure and modulate vascular resistance... (Review)
Review
The cardiovascular response to exercise is largely determined by neurocirculatory control mechanisms that help to raise blood pressure and modulate vascular resistance which, in concert with regional vasodilatory mechanisms, promote blood flow to active muscle and organs. These neurocirculatory control mechanisms include a feedforward mechanism, known as central command, and three feedback mechanisms, namely, ) the baroreflex, ) the exercise pressor reflex, and ) the arterial chemoreflex. The hemodynamic consequences of these control mechanisms result from their influence on the autonomic nervous system and subsequent alterations in cardiac output and vascular resistance. Although stimulation of the baroreflex inhibits sympathetic outflow and facilitates parasympathetic activity, central command, the exercise pressor reflex, and the arterial chemoreflex facilitate sympathetic activation and inhibit parasympathetic drive. Despite considerable understanding of the cardiovascular consequences of each of these mechanisms in isolation, the circulatory impact of their interaction, which occurs when various control systems are simultaneously activated (e.g., during exercise at altitude), has only recently been recognized. Although aging and cardiovascular disease (e.g., heart failure, hypertension) have both been recognized to alter the hemodynamic consequences of these regulatory systems, this review is limited to provide a brief overview on the action and interaction of neurocirculatory control mechanisms in health.
Topics: Muscle, Skeletal; Autonomic Nervous System; Baroreflex; Exercise; Blood Pressure; Arteries; Sympathetic Nervous System
PubMed: 37505474
DOI: 10.1152/ajpheart.00303.2023 -
Neuroscience Bulletin Dec 2023Breathing is an intrinsic natural behavior and physiological process that maintains life. The rhythmic exchange of gases regulates the delicate balance of chemical... (Review)
Review
Breathing is an intrinsic natural behavior and physiological process that maintains life. The rhythmic exchange of gases regulates the delicate balance of chemical constituents within an organism throughout its lifespan. However, chronic airway diseases, including asthma and chronic obstructive pulmonary disease, affect millions of people worldwide. Pathological airway conditions can disrupt respiration, causing asphyxia, cardiac arrest, and potential death. The innervation of the respiratory tract and the action of the immune system confer robust airway surveillance and protection against environmental irritants and pathogens. However, aberrant activation of the immune system or sensitization of the nervous system can contribute to the development of autoimmune airway disorders. Transient receptor potential ion channels and voltage-gated Na channels play critical roles in sensing noxious stimuli within the respiratory tract and interacting with the immune system to generate neurogenic inflammation and airway hypersensitivity. Although recent studies have revealed the involvement of nociceptor neurons in airway diseases, the further neural circuitry underlying airway protection remains elusive. Unraveling the mechanism underpinning neural circuit regulation in the airway may provide precise therapeutic strategies and valuable insights into the management of airway diseases.
Topics: Humans; Pulmonary Disease, Chronic Obstructive; Neurons; Respiration; Hypersensitivity; Reflex
PubMed: 37606821
DOI: 10.1007/s12264-023-01104-y -
La Tunisie Medicale Dec 2023A relatively common oral health problem, gag reflex is a clinical challenge during dentures fabrication. In the current literature several techniques have been described...
A relatively common oral health problem, gag reflex is a clinical challenge during dentures fabrication. In the current literature several techniques have been described regarding this clinical condition. The latter use either psychological, pharmacological and prosthetic therapies to treat these patients. The purpose of this case report is to highlight an original prosthetic strategy which consists on a progressive lengthening of the maxillary complete prosthesis allowing a patient with acute gag reflex to adapt to the denture palatal extension.
Topics: Humans; Denture, Complete, Upper; Denture Design; Denture Retention; Reflex
PubMed: 38477203
DOI: No ID Found -
Journal of Neurophysiology Jul 2023In 1998, I was asked by the American Physiological Society to review a book written by Dr. Michael de Burgh Daly, . Inspired by this work, I came to appreciate how... (Review)
Review
In 1998, I was asked by the American Physiological Society to review a book written by Dr. Michael de Burgh Daly, . Inspired by this work, I came to appreciate how researchers in the later stages of their careers and who provide a detailed review of their experimental approach might effectively contribute to science, especially to the benefit of young scientists (Yu J. 41: 231, 1998.). This article is written in that vein. Over several decades of intensive investigation of cardiopulmonary reflexes, focused on the sensory receptors, my colleagues and I advanced a novel multiple-sensor theory (MST) to explain the role of the vagal mechanosensory system. Described here is our research journey through various stages of developing MST and the process of how the problem was identified, approached, and tackled. MST redefines conventional mechanosensor doctrines and is supported by new studies that clarify a century of research data. It entails reinterpretation of many established findings. Hopefully, this article will benefit young scientists, such as graduate and postdoctoral students in the cardiopulmonary sensory research field.
Topics: Humans; Heart; Vagus Nerve; Lung; Reflex; Chemoreceptor Cells
PubMed: 37341418
DOI: 10.1152/jn.00062.2023 -
Clinical Neurophysiology : Official... May 2024Blinking is a motor act characterized by the sequential closing and opening of the eyelids, which is achieved through the reciprocal activation of the orbicularis oculi... (Review)
Review
Blinking is a motor act characterized by the sequential closing and opening of the eyelids, which is achieved through the reciprocal activation of the orbicularis oculi and levator palpebrae superioris muscles. This stereotyped movement can be triggered reflexively, occur spontaneously, or voluntarily initiated. During each type of blinking, the neural control of the antagonistic interaction between the orbicularis oculi and levator palpebrae superioris muscles is governed by partially overlapping circuits distributed across cortical, subcortical, and brainstem structures. This paper provides a comprehensive overview of the anatomical and physiological foundations underlying the neural control of blinking. We describe the infra-nuclear apparatus, as well as the supra-nuclear control mechanisms, i.e., how cortical, subcortical, and brainstem structures regulate and coordinate the different types of blinking.
Topics: Humans; Blinking; Animals; Brain Stem; Eyelids
PubMed: 38447495
DOI: 10.1016/j.clinph.2024.02.023 -
Neurology India 2023
Topics: Humans; Urination; Epilepsy, Reflex; Reflex
PubMed: 38174496
DOI: 10.4103/0028-3886.391379 -
Revista Portuguesa de Cardiologia :... Sep 2023
Topics: Humans; Syncope; Reflex; Syncope, Vasovagal
PubMed: 37023980
DOI: 10.1016/j.repc.2023.04.001 -
Physiological Research Dec 2023Cough is one of the most important airway defensive reflexes aimed at removing foreign particles or endogenously produced materials from the airways and provides... (Review)
Review
Cough is one of the most important airway defensive reflexes aimed at removing foreign particles or endogenously produced materials from the airways and provides protection against aspiration. Generally considered, cough is a vital physiological defensive mechanism for lung health. However, in case of cough dysregulation this reflex can become pathological and leads to an adverse influence on daily life. Therefore, it is necessary to effectively evaluate the severity of cough for its diagnosis and treatment. There are subjective and objective methods for assessing cough. These methods should help describe the heterogeneity of cough phenotypes and may establish better treatment by monitoring response to nonpharmacological or pharmacological therapies. It is important to keep in mind that the clinical assessment of cough should include both tools that measure the amount and severity of the cough. The importance of a combined subjective and objective evaluation for a comprehensive assessment of cough has been advocated in the guidelines of the European Respiratory Society on cough evaluation. This review article provides an overview of subjective and objective methods for assessing and monitoring cough in children and adults comparing to animal models. Key words Cough frequency; Cough intensity; Cough reflex sensitivity; Cough monitors; Cough assessment.
Topics: Animals; Adult; Child; Humans; Cough; Lung; Reflex
PubMed: 38215057
DOI: 10.33549/physiolres.935062 -
The Journal of Hand Surgery Jun 2024The sensory-collapse test (formerly the scratch-collapse test) is a physical examination finding describing a momentary inhibition of external shoulder rotation... (Review)
Review
The sensory-collapse test (formerly the scratch-collapse test) is a physical examination finding describing a momentary inhibition of external shoulder rotation following light stimulation of an injured nerve in the ipsilateral limb. Similar to other physical examination tests designed to interrogate nerve compression, such as the Phalen or Tinel tests, its test characteristics demonstrate variation. There remains speculation about the test's existence and anatomic basis. The literature of mammalian reflex physiology was reviewed with an emphasis on the sensory pathways from the upper extremity, the extrapyramidal system, and newly discovered pathways and concepts of nociception. A clear reflex pathway is described connecting the stimulus within an injured nerve through the afferent pathways in the fasciculus cuneatus in the spinal cord directly to the lateral reticulospinal tract, resulting in the inhibition of extensor muscles in the proximal limb (eg, shoulder) and activation of the limb flexors by acting upon alpha and gamma motor neurons. The sensory-collapse test represents a reflex pathway that teleologically provides a mechanism to protect an injured nerve by withdrawal toward the trunk and away from the noxious environment.
Topics: Humans; Reflex; Nerve Compression Syndromes; Nociception; Peripheral Nerve Injuries; Afferent Pathways
PubMed: 38456864
DOI: 10.1016/j.jhsa.2024.01.017