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Journal of Neurophysiology Dec 2017Large-diameter myelinated phrenic afferents discharge in phase with diaphragm contraction, and smaller diameter fibers discharge across the respiratory cycle. In this... (Review)
Review
Large-diameter myelinated phrenic afferents discharge in phase with diaphragm contraction, and smaller diameter fibers discharge across the respiratory cycle. In this article, we review the phrenic afferent literature and highlight areas in need of further study. We conclude that ) activation of both myelinated and nonmyelinated phrenic sensory afferents can influence respiratory motor output on a breath-by-breath basis; ) the relative impact of phrenic afferents substantially increases with diaphragm work and fatigue; ) activation of phrenic afferents has a powerful impact on sympathetic motor outflow, and ) phrenic afferents contribute to diaphragm somatosensation and the conscious perception of breathing. Much remains to be learned regarding the spinal and supraspinal distribution and synaptic contacts of myelinated and nonmyelinated phrenic afferents. Similarly, very little is known regarding the potential role of phrenic afferent neurons in triggering or modulating expression of respiratory neuroplasticity.
Topics: Animals; Diaphragm; Humans; Neuronal Plasticity; Neurons, Afferent; Nociception; Phrenic Nerve; Respiration
PubMed: 28835527
DOI: 10.1152/jn.00484.2017 -
Cell Oct 2020Ophthalmic, maxillary, and mandibular branches of the trigeminal nerve provide sensory innervation to orofacial tissues. Trigeminal sensory neurons respond to a diverse...
Ophthalmic, maxillary, and mandibular branches of the trigeminal nerve provide sensory innervation to orofacial tissues. Trigeminal sensory neurons respond to a diverse array of sensory stimuli to generate distinct sensations, including thermosensation, mechanosensation, itching, and pain. These sensory neurons also detect the distinct sharpness or pungency of many foods and beverages. This SnapShot highlights the transduction ion channels critical to orofacial sensation.
Topics: Cranial Nerves; Humans; Neurons, Afferent; Pain; Sensation; Trigeminal Nerve
PubMed: 33007264
DOI: 10.1016/j.cell.2020.08.014 -
Neurourology and Urodynamics Feb 2016To present a synopsis of the presentations and discussions from Think Tank I, "Implications for afferent-urothelial bidirectional communication" of the 2014... (Review)
Review
AIMS
To present a synopsis of the presentations and discussions from Think Tank I, "Implications for afferent-urothelial bidirectional communication" of the 2014 International Consultation on Incontinence-Research Society (ICI-RS) meeting in Bristol, UK.
METHODS
The participants presented what is new, currently understood or still unknown on afferent-urothelial signaling mechanisms. New avenues of research and experimental methodologies that are or could be employed were presented and discussed.
RESULTS
It is clear that afferent-urothelial interactions are integral to the regulation of normal bladder function and that its disruption can have detrimental consequences. The urothelium is capable of releasing numerous signaling factors that can affect sensory neurons innervating the suburothelium. However, the understanding of how factors released from urothelial cells and afferent nerve terminals regulate one another is incomplete. Utilization of techniques such as viruses that genetically encode Ca(2+) sensors, based on calmodulin and green fluorescent protein, has helped to address the cellular mechanisms involved. Additionally, the epithelial-neuronal interactions in the urethra may also play a significant role in lower urinary tract regulation and merit further investigation.
CONCLUSION
The signaling capabilities of the urothelium and afferent nerves are well documented, yet how these signals are integrated to regulate bladder function is unclear. There is unquestionably a need for expanded methodologies to further our understanding of lower urinary tract sensory mechanisms and their contribution to various pathologies.
Topics: Animals; Congresses as Topic; Epithelial Cells; Humans; Neurons, Afferent; Neurons, Efferent; Synaptic Transmission; Urinary Bladder; Urothelium
PubMed: 26872567
DOI: 10.1002/nau.22839 -
Journal of Neurophysiology Sep 2022Integrative functions of spinal interneurons are well recognized but the relative role of different interneuronal populations in this process continues to be... (Review)
Review
Integrative functions of spinal interneurons are well recognized but the relative role of different interneuronal populations in this process continues to be investigated. It therefore appeared useful to review the principles of integration of afferent information by the interneurons analyzed so far as these principles should apply also to those remaining to be analyzed. Considering the results of both functional and morphological studies of spinal interneurons and of the morphology and immunochemistry of afferent fibers that provide input to them, the following five basic principles of processing of afferent information by them will be outlined; ) afferent information of any origin is forwarded to several neuronal populations, ) information from any sources of input is distributed unevenly, ) input from several sources is integrated by individual neurons as well as by their populations, ) specific combinations of input are integrated by different neuronal populations, and ) afferent input to spinal interneurons is only one of the features distinguishing their functional populations. As the spinal neuronal organization and properties of neurons and afferent fibers in the so far investigated species (cat, rodents, and primates) have been found to resemble, future studies using molecular techniques in the mouse should allow the new data to integrate with those of the preceding studies and the principles outlined earlier as well as any new ones should apply also in humans.
Topics: Afferent Pathways; Animals; Humans; Interneurons; Mice; Neurons, Afferent; Spinal Cord
PubMed: 36043802
DOI: 10.1152/jn.00344.2022 -
Current Opinion in Neurobiology Jun 2022The muscle spindle (MS) provides essential sensory information for motor control and proprioception. The Group Ia and II MS afferents are low threshold slowly-adapting... (Review)
Review
The muscle spindle (MS) provides essential sensory information for motor control and proprioception. The Group Ia and II MS afferents are low threshold slowly-adapting mechanoreceptors and report both static muscle length and dynamic muscle movement information. The exact molecular mechanism by which MS afferents transduce muscle movement into action potentials is incompletely understood. This short review will discuss recent evidence suggesting that PIEZO2 is an essential mechanically sensitive ion channel in MS afferents and that vesicle-released glutamate contributes to maintaining afferent excitability during the static phase of stretch. Other mechanically gated ion channels, voltage-gated sodium channels, other ion channels, regulatory proteins, and interactions with the intrafusal fibers are also important for MS afferent mechanosensation. Future studies are needed to fully understand mechanosensation in the MS and whether different complements of molecular mediators contribute to the different response properties of Group Ia and II afferents.
Topics: Action Potentials; Ion Channels; Mechanoreceptors; Muscle Spindles; Neurons, Afferent; Proprioception
PubMed: 35430481
DOI: 10.1016/j.conb.2022.102542 -
PLoS Computational Biology Dec 2022Sensory information is conveyed by populations of neurons, and coding strategies cannot always be deduced when considering individual neurons. Moreover, information...
Sensory information is conveyed by populations of neurons, and coding strategies cannot always be deduced when considering individual neurons. Moreover, information coding depends on the number of neurons available and on the composition of the population when multiple classes with different response properties are available. Here, we study population coding in human tactile afferents by employing a recently developed simulator of mechanoreceptor firing activity. First, we highlight the interplay of afferents within each class. We demonstrate that the optimal afferent density to convey maximal information depends on both the tactile feature under consideration and the afferent class. Second, we find that information is spread across different classes for all tactile features and that each class encodes both redundant and complementary information with respect to the other afferent classes. Specifically, combining information from multiple afferent classes improves information transmission and is often more efficient than increasing the density of afferents from the same class. Finally, we examine the importance of temporal and spatial contributions, respectively, to the joint spatiotemporal code. On average, destroying temporal information is more destructive than removing spatial information, but the importance of either depends on the stimulus feature analyzed. Overall, our results suggest that both optimal afferent innervation densities and the composition of the population depend in complex ways on the tactile features in question, potentially accounting for the variety in which tactile peripheral populations are assembled in different regions across the body.
Topics: Humans; Action Potentials; Touch; Mechanoreceptors; Neurons; Neurons, Afferent
PubMed: 36477028
DOI: 10.1371/journal.pcbi.1010763 -
American Journal of Physiology.... Sep 2019The potential role of the intestinal microbiota in modulating visceral pain has received increasing attention during recent years. This has led to the identification of... (Review)
Review
The potential role of the intestinal microbiota in modulating visceral pain has received increasing attention during recent years. This has led to the identification of signaling pathways that have been implicated in communication between gut bacteria and peripheral pain pathways. In addition to the well-characterized impact of the microbiota on the immune system, which in turn affects nociceptor excitability, bacteria can modulate visceral afferent pathways by effects on enterocytes, enteroendocrine cells, and the neurons themselves. Proteases produced by bacteria, or by host cells in response to bacteria, can increase or decrease the excitability of nociceptive dorsal root ganglion (DRG) neurons depending on the receptor activated. Short-chain fatty acids generated by colonic bacteria are involved in gut-brain communication, and intracolonic short-chain fatty acids have pronociceptive effects in rodents but may be antinociceptive in humans. Gut bacteria modulate the synthesis and release of enteroendocrine cell mediators, including serotonin and glucagon-like peptide-1, which activate extrinsic afferent neurons. Deciphering the complex interactions between visceral afferent neurons and the gut microbiota may lead to the development of improved probiotic therapies for visceral pain.
Topics: Animals; Colon; Ganglia, Spinal; Gastrointestinal Microbiome; Humans; Microbiota; Neurons, Afferent; Visceral Pain
PubMed: 31290688
DOI: 10.1152/ajpgi.00052.2019 -
Peptides Nov 2020Estrogens modulate different physiological functions, including reproduction, inflammation, bone formation, energy expenditure, and food intake. In this review, we... (Review)
Review
Estrogens modulate different physiological functions, including reproduction, inflammation, bone formation, energy expenditure, and food intake. In this review, we highlight the effect of estrogens on food intake regulation and the latest literature on intracellular estrogen signaling. In addition, gut satiety hormones, such as cholecystokinin, glucagon-like peptide 1 and leptin are essential to regulate ingestive behaviors in the postprandial period. These peripheral signals are sensed by vagal afferent terminals in the gut wall and transmitted to the hindbrain axis. Here we 1. review the role of the vagus-hindbrain axis in response to gut satiety signals and 2. consider the potential synergistic effects of estrogens on gut satiety signals at the level of vagal afferent neurons and nuclei located in the hindbrain. Understanding the action of estrogens in gut-brain axis provides a potential strategy to develop estrogen-based therapies for metabolic diseases and emphasizes the importance of sex difference in the treatment of obesity.
Topics: Animals; Cholecystokinin; Eating; Energy Metabolism; Estrogens; Female; Gastrointestinal Hormones; Glucagon-Like Peptide 1; Humans; Leptin; Male; Neurons, Afferent; Receptors, Estrogen; Rhombencephalon; Satiety Response; Vagus Nerve
PubMed: 32860834
DOI: 10.1016/j.peptides.2020.170389 -
Advances in Nutrition (Bethesda, Md.) Jul 2014It is well established that food intake behavior and energy balance are regulated by crosstalk between peripheral organ systems and the central nervous system (CNS), for... (Review)
Review
It is well established that food intake behavior and energy balance are regulated by crosstalk between peripheral organ systems and the central nervous system (CNS), for instance, through the actions of peripherally derived leptin on hindbrain and hypothalamic loci. Diet- or obesity-associated disturbances in metabolic and hormonal signals to the CNS can perturb metabolic homeostasis bodywide. Although interrelations between metabolic status and diet with CNS biology are well characterized, afferent networks (those sending information to the CNS from the periphery) have received far less attention. It is increasingly appreciated that afferent neurons in adipose tissue, the intestines, liver, and other tissues are important controllers of energy balance and feeding behavior. Disruption in their signaling may have consequences for cardiovascular, pancreatic, adipose, and immune function. This review discusses the diverse ways that afferent neurons participate in metabolic homeostasis and highlights how changes in their function associate with dysmetabolic states, such as obesity and insulin resistance.
Topics: Animals; Diet; Energy Intake; Energy Metabolism; Feeding Behavior; Homeostasis; Humans; Insulin Resistance; Metabolic Diseases; Neurons, Afferent; Obesity
PubMed: 25022988
DOI: 10.3945/an.113.005439 -
Frontiers in Neural Circuits 2022
Topics: Visual Perception; Neurons, Afferent
PubMed: 36712836
DOI: 10.3389/fncir.2022.1129196