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Neuron Feb 2022The vagus nerve is an indispensable body-brain connection that controls vital aspects of autonomic physiology like breathing, heart rate, blood pressure, and gut... (Review)
Review
The vagus nerve is an indispensable body-brain connection that controls vital aspects of autonomic physiology like breathing, heart rate, blood pressure, and gut motility, reflexes like coughing and swallowing, and survival behaviors like feeding, drinking, and sickness responses. Classical physiological studies and recent molecular/genetic approaches have revealed a tremendous diversity of vagal sensory neuron types that innervate different internal organs, with many cell types remaining poorly understood. Here, we review the state of knowledge related to vagal sensory neurons that innervate the respiratory, cardiovascular, and digestive systems. We focus on cell types and their response properties, physiological/behavioral roles, engaged neural circuits and, when possible, sensory receptors. We are only beginning to understand the signal transduction mechanisms used by vagal sensory neurons and upstream sentinel cells, and future studies are needed to advance the field of interoception to the level of mechanistic understanding previously achieved for our external senses.
Topics: Interoception; Reflex; Sensation; Sensory Receptor Cells; Vagus Nerve
PubMed: 35051375
DOI: 10.1016/j.neuron.2021.12.020 -
Journal of Biomedical Science Dec 2021Addictive drugs are habit-forming. Addiction is a learned behavior; repeated exposure to addictive drugs can stamp in learning. Dopamine-depleted or dopamine-deleted... (Review)
Review
Addictive drugs are habit-forming. Addiction is a learned behavior; repeated exposure to addictive drugs can stamp in learning. Dopamine-depleted or dopamine-deleted animals have only unlearned reflexes; they lack learned seeking and learned avoidance. Burst-firing of dopamine neurons enables learning-long-term potentiation (LTP)-of search and avoidance responses. It sets the stage for learning that occurs between glutamatergic sensory inputs and GABAergic motor-related outputs of the striatum; this learning establishes the ability to search and avoid. Independent of burst-firing, the rate of single-spiking-or "pacemaker firing"-of dopaminergic neurons mediates motivational arousal. Motivational arousal increases during need states and its level determines the responsiveness of the animal to established predictive stimuli. Addictive drugs, while usually not serving as an external stimulus, have varying abilities to activate the dopamine system; the comparative abilities of different addictive drugs to facilitate LTP is something that might be studied in the future.
Topics: Animals; Appetitive Behavior; Avoidance Learning; Behavior, Addictive; Dopamine; Dopaminergic Neurons; Learning; Long-Term Potentiation; Mice; Rats; Reflex
PubMed: 34852810
DOI: 10.1186/s12929-021-00779-7 -
Physiology (Bethesda, Md.) Mar 2016Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated... (Review)
Review
Drowning physiology relates to two different events: immersion (upper airway above water) and submersion (upper airway under water). Immersion involves integrated cardiorespiratory responses to skin and deep body temperature, including cold shock, physical incapacitation, and hypovolemia, as precursors of collapse and submersion. The physiology of submersion includes fear of drowning, diving response, autonomic conflict, upper airway reflexes, water aspiration and swallowing, emesis, and electrolyte disorders. Submersion outcome is determined by cardiac, pulmonary, and neurological injury. Knowledge of drowning physiology is scarce. Better understanding may identify methods to improve survival, particularly related to hot-water immersion, cold shock, cold-induced physical incapacitation, and fear of drowning.
Topics: Animals; Cold Temperature; Diving; Drowning; Heart; Humans; Reflex; Water
PubMed: 26889019
DOI: 10.1152/physiol.00002.2015 -
Cell Reports. Medicine Jul 2022The cholinergic anti-inflammatory pathway is the efferent arm of the inflammatory reflex, a neural circuit through which the CNS can modulate peripheral immune... (Review)
Review
The cholinergic anti-inflammatory pathway is the efferent arm of the inflammatory reflex, a neural circuit through which the CNS can modulate peripheral immune responses. Signals communicated via the vagus and splenic nerves use acetylcholine, produced by Choline acetyltransferase (ChAT)+ T cells, to downregulate the inflammatory actions of macrophages expressing α7 nicotinic receptors. Pre-clinical studies using transgenic animals, cholinergic agonists, vagotomy, and vagus nerve stimulation have demonstrated this pathway's role and therapeutic potential in numerous inflammatory diseases. In this review, we summarize what is understood about the inflammatory reflex. We also demonstrate how pre-clinical findings are being translated into promising clinical trials, and we draw particular attention to innovative bioelectronic methods of harnessing the cholinergic anti-inflammatory pathway for clinical use.
Topics: Animals; Neuroimmunomodulation; Reflex; Vagus Nerve; Vagus Nerve Stimulation; alpha7 Nicotinic Acetylcholine Receptor
PubMed: 35858588
DOI: 10.1016/j.xcrm.2022.100696 -
Current Biology : CB Sep 2020Many of us know about stretch reflexes from the doctor's office, when a physician taps the tendon near our kneecap to elicit a quick knee extension. This procedure is...
Many of us know about stretch reflexes from the doctor's office, when a physician taps the tendon near our kneecap to elicit a quick knee extension. This procedure is used as a diagnostic tool to determine the integrity of the spinal cord and the extension response it elicits may seem otherwise useless. In fact, the tendon tap taps into one aspect of a critical building block of mammalian motor control, the stretch reflexes. Stretch reflexes are often thought to quickly resist unexpected changes in muscle length via a very simple circuit in the spinal cord, and this is one circuit that the tendon tap engages. It turns out, however, that stretch reflexes support a myriad of functions and are highly flexible. Under naturalistic conditions, stretch reflexes are shaped by peripheral physiology and engage neural circuits spanning the spinal cord, brainstem and cerebral cortex. In this Primer, we outline what is currently known about stretch reflex function and its underlying mechanisms, with a specific focus on how the cascade of nested responses collectively known as stretch reflexes interact with and build off of one another to support real-world motor behavior.
Topics: Humans; Motor Activity; Muscle, Skeletal; Reaction Time; Reflex, Stretch; Tendons
PubMed: 32961152
DOI: 10.1016/j.cub.2020.07.092 -
Journal of Immunology (Baltimore, Md. :... May 2017The field of immunology is principally focused on the molecular mechanisms by which hematopoietic cells initiate and maintain innate and adaptive immunity. That... (Review)
Review
The field of immunology is principally focused on the molecular mechanisms by which hematopoietic cells initiate and maintain innate and adaptive immunity. That cornerstone of attention has been expanded by recent discoveries that neuronal signals occupy a critical regulatory niche in immunity. The discovery is that neuronal circuits operating reflexively regulate innate and adaptive immunity. One particularly well-characterized circuit regulating innate immunity, the inflammatory reflex, is dependent upon action potentials transmitted to the reticuloendothelial system via the vagus and splenic nerves. This field has grown significantly with the identification of several other reflexes regulating discrete immune functions. As outlined in this review, the delineation of these mechanisms revealed a new understanding of immunity, enabled a first-in-class clinical trial using bioelectronic devices to inhibit cytokines and inflammation in rheumatoid arthritis patients, and provided a mosaic view of immunity as the integration of hematopoietic and neural responses to infection and injury.
Topics: Adaptive Immunity; Allergy and Immunology; Animals; Cytokines; Humans; Immunity, Innate; Neurogenic Inflammation; Neuroimmunomodulation; Neurosciences; Reflex; Spleen; Vagus Nerve
PubMed: 28416717
DOI: 10.4049/jimmunol.1601613 -
Physiological Research Mar 2020Since the recognition of angiotensin-converting enzyme inhibitors (ACEIs)-induced cough, drug has been considered as a potential cause of chronic cough. This review... (Review)
Review
Since the recognition of angiotensin-converting enzyme inhibitors (ACEIs)-induced cough, drug has been considered as a potential cause of chronic cough. This review presents recent knowledge on drug-induced coughs in patients with chronic cough. The focus is placed on ACEIs, for which there are a multitude of studies documenting their associations with cough. Additional drugs are discussed for which there are reports of cough as a side effect of treatment, and the potential mechanisms of these effects are discussed.
Topics: Analgesics, Opioid; Angiotensin-Converting Enzyme Inhibitors; Animals; Calcium Channel Blockers; Chronic Disease; Cough; Fentanyl; Humans; Reflex
PubMed: 32228014
DOI: 10.33549/physiolres.934406 -
Progress in Brain Research 2015An operant-conditioning protocol that bases reward on the electromyographic response produced by a specific CNS pathway can change that pathway. For example, in both... (Review)
Review
An operant-conditioning protocol that bases reward on the electromyographic response produced by a specific CNS pathway can change that pathway. For example, in both animals and people, an operant-conditioning protocol can increase or decrease the spinal stretch reflex or its electrical analog, the H-reflex. Reflex change is associated with plasticity in the pathway of the reflex as well as elsewhere in the spinal cord and brain. Because these pathways serve many different behaviors, the plasticity produced by this conditioning can change other behaviors. Thus, in animals or people with partial spinal cord injuries, appropriate reflex conditioning can improve locomotion. Furthermore, in people with spinal cord injuries, appropriate reflex conditioning can trigger widespread beneficial plasticity. This wider plasticity appears to reflect an iterative process through which the multiple behaviors in the individual's repertoire negotiate the properties of the spinal neurons and synapses that they all use. Operant-conditioning protocols are a promising new therapeutic method that could complement other rehabilitation methods and enhance functional recovery. Their successful use requires strict adherence to appropriately designed procedures, as well as close attention to accommodating and engaging the individual subject in the conditioning process.
Topics: Animals; Conditioning, Operant; H-Reflex; Humans; Neuronal Plasticity; Recovery of Function; Reflex, Stretch; Spinal Cord Injuries
PubMed: 25890136
DOI: 10.1016/bs.pbr.2015.02.002 -
Current Opinion in Neurology Feb 2019Bilateral vestibular deficits exist and their prevalence is more important than believed by the medical community. Their severe impact has inspired several teams to... (Review)
Review
PURPOSE OF REVIEW
Bilateral vestibular deficits exist and their prevalence is more important than believed by the medical community. Their severe impact has inspired several teams to develop technical solutions in an attempt to rehabilitate patients. A particularly promising pathway is the vestibular implant. This article describes the main milestones in this field, mainly focusing on work conducted in human patients.
RECENT FINDINGS
There have been substantial research efforts, first in animals and more recently in humans, toward the development of vestibular implants. Humans have demonstrated surprising adaptation capabilities to the artificial vestibular signal. Today, the possibility of restoring vestibular reflexes, particularly the vestibulo-ocular reflex, and even achieving useful function in close-to-reality tasks (i.e. improving visual abilities while walking) have been demonstrated in humans.
SUMMARY
The vestibular implant opens new perspectives, not only as an effective therapeutic tool, but also pushes us to go beyond current knowledge and well-established clinical concepts.
Topics: Adaptation, Physiological; Animals; Humans; Prostheses and Implants; Reflex, Vestibulo-Ocular; Vestibular Diseases; Vestibule, Labyrinth
PubMed: 30566413
DOI: 10.1097/WCO.0000000000000639 -
Neuroscience Letters Apr 2019While thermosensation from external environment has been extensively studied, physiological responses to temperature changes inside the body and the underlying... (Review)
Review
While thermosensation from external environment has been extensively studied, physiological responses to temperature changes inside the body and the underlying regulatory mechanisms are less understood. As a critical link between body and brain that relays visceral organ information and regulates numerous physiological functions, the vagus nerve has been proposed to mediate diverse visceral thermal reflexes and indirectly regulate body temperature. However, the precise role of the vagus nerve in body thermal responses or visceral organ-related thermoregulation is still under debate due to extensive contradictory results. This data discrepancy is likely due to the high cell heterogeneity in the vagus nerve, as diverse vagal neuron types mediate numerous and sometimes opposite physiological functions. Here, we will review evidences that support and against the role of the vagus nerve in body thermosensation and thermoregulation and discuss potential future approaches for better understanding of this critical issue.
Topics: Animals; Body Temperature; Body Temperature Regulation; Energy Metabolism; Humans; Neurons; Reflex; Vagus Nerve
PubMed: 30634012
DOI: 10.1016/j.neulet.2019.01.013