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Neuron Sep 2015Recent advances have clarified how the brain detects CO2 to regulate breathing (central respiratory chemoreception). These mechanisms are reviewed and their significance... (Review)
Review
Recent advances have clarified how the brain detects CO2 to regulate breathing (central respiratory chemoreception). These mechanisms are reviewed and their significance is presented in the general context of CO2/pH homeostasis through breathing. At rest, respiratory chemoreflexes initiated at peripheral and central sites mediate rapid stabilization of arterial PCO2 and pH. Specific brainstem neurons (e.g., retrotrapezoid nucleus, RTN; serotonergic) are activated by PCO2 and stimulate breathing. RTN neurons detect CO2 via intrinsic proton receptors (TASK-2, GPR4), synaptic input from peripheral chemoreceptors and signals from astrocytes. Respiratory chemoreflexes are arousal state dependent whereas chemoreceptor stimulation produces arousal. When abnormal, these interactions lead to sleep-disordered breathing. During exercise, central command and reflexes from exercising muscles produce the breathing stimulation required to maintain arterial PCO2 and pH despite elevated metabolic activity. The neural circuits underlying central command and muscle afferent control of breathing remain elusive and represent a fertile area for future investigation.
Topics: Animals; Carbon Dioxide; Chemoreceptor Cells; Homeostasis; Humans; Respiration; Respiratory Center
PubMed: 26335642
DOI: 10.1016/j.neuron.2015.08.001 -
Genetics Mar 2021Chemosensory neurons translate perception of external chemical cues, including odorants, tastants, and pheromones, into information that drives attraction or avoidance... (Review)
Review
Chemosensory neurons translate perception of external chemical cues, including odorants, tastants, and pheromones, into information that drives attraction or avoidance motor programs. In the laboratory, robust behavioral assays, coupled with powerful genetic, molecular and optical tools, have made Caenorhabditis elegans an ideal experimental system in which to dissect the contributions of individual genes and neurons to ethologically relevant chemosensory behaviors. Here, we review current knowledge of the neurons, signal transduction molecules and regulatory mechanisms that underlie the response of C. elegans to chemicals, including pheromones. The majority of identified molecules and pathways share remarkable homology with sensory mechanisms in other organisms. With the development of new tools and technologies, we anticipate that continued study of chemosensory signal transduction and processing in C. elegans will yield additional new insights into the mechanisms by which this animal is able to detect and discriminate among thousands of chemical cues with a limited sensory neuron repertoire.
Topics: Animals; Behavior, Animal; Caenorhabditis elegans; Chemoreceptor Cells; Neuronal Plasticity; Signal Transduction
PubMed: 33693646
DOI: 10.1093/genetics/iyab004 -
Trends in Neurosciences Nov 2019The ventral surface of the rostral medulla oblongata has been suspected since the 1960s to harbor central respiratory chemoreceptors [i.e., acid-activated neurons that... (Review)
Review
The ventral surface of the rostral medulla oblongata has been suspected since the 1960s to harbor central respiratory chemoreceptors [i.e., acid-activated neurons that regulate breathing to maintain a constant arterial PCO (PaCO)]. The key neurons, a.k.a. the retrotrapezoid nucleus (RTN), have now been identified. In this review we describe their transcriptome, developmental lineage, and anatomical projections. We also review their contribution to CO homeostasis and to the regulation of breathing automaticity during sleep and wake. Finally, we discuss several mechanisms that contribute to the activation of RTN neurons by COin vivo: cell-autonomous effects of protons; paracrine effects of pH mediated by surrounding astrocytes and blood vessels; and excitatory inputs from other CO-responsive CNS neurons.
Topics: Animals; Carbon Dioxide; Chemoreceptor Cells; Homeostasis; Humans; Hypercapnia; Hypoxia; Medulla Oblongata; Neurons; Respiration; Sleep
PubMed: 31635852
DOI: 10.1016/j.tins.2019.09.002 -
Advances in Experimental Medicine and... 2012The retrotrapezoid nucleus (RTN) is located in the rostral medulla oblongata close to the ventral surface and consists of a bilateral cluster of glutamatergic neurons... (Review)
Review
The retrotrapezoid nucleus (RTN) is located in the rostral medulla oblongata close to the ventral surface and consists of a bilateral cluster of glutamatergic neurons that are non-aminergic and express homeodomain transcription factor Phox2b throughout life. These neurons respond vigorously to increases in local pCO(2) via cell-autonomous and paracrine (glial) mechanisms and receive additional chemosensory information from the carotid bodies. RTN neurons exclusively innervate the regions of the brainstem that contain the respiratory pattern generator (RPG). Lesion or inhibition of RTN neurons largely attenuates the respiratory chemoreflex of adult rats whereas their activation increases respiratory rate, inspiratory amplitude and active expiration. Phox2b mutations that cause congenital central hypoventilation syndrome in humans prevent the development of RTN neurons in mice. Selective deletion of the RTN Phox2b-VGLUT2 neurons by genetic means in mice eliminates the respiratory chemoreflex in neonates.In short, RTN Phox2b-VGLUT2 neurons are a major nodal point of the CNS network that regulates pCO(2) via breathing and these cells are probable central chemoreceptors.
Topics: Animals; Carbon Dioxide; Chemoreceptor Cells; Homeodomain Proteins; Humans; Medulla Oblongata; Reflex; Respiration; Transcription Factors; Vesicular Glutamate Transport Protein 2
PubMed: 23080151
DOI: 10.1007/978-94-007-4584-1_16 -
Pflugers Archiv : European Journal of... May 2015Two-pore domain K(+) (K2P) channels are involved in a variety of physiological processes by virtue of their high basal activity and sensitivity to various biological... (Review)
Review
Two-pore domain K(+) (K2P) channels are involved in a variety of physiological processes by virtue of their high basal activity and sensitivity to various biological stimuli. One of these processes is secretion of hormones and transmitters in response to stimuli such as hypoxia, acidosis, and receptor agonists. The rise in intracellular [Ca(2+)] ([Ca(2+)]i) that is critical for the secretory event can be achieved by several mechanisms: (a) inhibition of resting (background) K(+) channels, (b) activation of Na(+)/Ca(2+)-permeable channels, and (c) release of Ca(2+) from intracellular stores. Here, we discuss the role of TASK and TREK in stimulus-secretion mechanisms in carotid body chemoreceptor cells and adrenal medullary/cortical cells. Studies show that stimuli such as hypoxia and acidosis cause cell depolarization and transmitter/hormone secretion by inhibition of TASK or TREK. Subsequent elevation of [Ca(2+)]i produced by opening of voltage-dependent Ca(2+) channels then activates a Na(+)-permeable cation channel, presumably to help sustain the depolarization and [Ca(2+)]i. Agonists such as angiotensin II may elevate [Ca(2+)]i via multiple mechanisms involving both inhibition of TASK/TREK and Ca(2+) release from internal stores to cause aldosterone secretion. Thus, inhibition of resting (background) K(+) channels and subsequent activation of voltage-gated Ca(2+) channels and Na(+)-permeable non-selective cation channels may be a common ionic mechanism that lead to hormone and transmitter secretion.
Topics: Adrenal Glands; Animals; Calcium; Carotid Body; Chemoreceptor Cells; Humans; Membrane Potentials; Potassium Channels, Tandem Pore Domain
PubMed: 25476848
DOI: 10.1007/s00424-014-1663-3 -
Clinical Journal of the American... Sep 2015In order to assess the status of the volume and composition of the body fluid compartment, the kidney monitors a wide variety of chemical and physical parameters. It has... (Review)
Review
In order to assess the status of the volume and composition of the body fluid compartment, the kidney monitors a wide variety of chemical and physical parameters. It has recently become clear that the kidney's sensory capacity extends well beyond its ability to sense ion concentrations in the forming urine. The kidney also keeps track of organic metabolites derived from a surprising variety of sources and uses a complex interplay of physical and chemical sensing mechanisms to measure the rate of fluid flow in the nephron. Recent research has provided new insights into the nature of these sensory mechanisms and their relevance to renal function.
Topics: Adenylyl Cyclases; Animals; Bicarbonates; Chemoreceptor Cells; Cilia; Fatty Acids, Volatile; Humans; Kidney; Mechanoreceptors; Succinic Acid
PubMed: 25280495
DOI: 10.2215/CJN.00730114 -
Molecular Microbiology Jul 2019Motile bacteria are proficient at finding optimal environments for colonization. Often, they use chemotaxis to sense nutrient availability and dangerous concentrations...
Motile bacteria are proficient at finding optimal environments for colonization. Often, they use chemotaxis to sense nutrient availability and dangerous concentrations of toxic chemicals. For many bacteria, the repertoire of chemoreceptors is large, suggesting they possess a broad palate with respect to sensing. However, knowledge of the molecules detected by chemotaxis signal transduction systems is limited. Some bacteria, like Vibrio parahaemolyticus, are social and swarm in groups on surfaces. This marine bacterium and human pathogen secretes the S signal autoinducer, which cues degradation of intracellular c-di-GMP leading to transcription of the swarming program. Here, we report that the S signal also directs motility at a behavioral level by serving as a chemoattractant. The data demonstrate that V. parahaemolyticus senses the S signal using SscL and SscS, homologous methyl-accepting chemotaxis proteins. SscL is required by planktonic bacteria for S signal chemotaxis. SscS plays a role during swarming, and mutants lacking this chemoreceptor swarm faster and produce colonies with more deeply branched swarming fronts than the wild type or the sscL mutant. Other Vibrio species can swim toward the S signal, suggesting a recruitment role for this cell-cell communication molecule in the context of polymicrobial marine communities.
Topics: Bacterial Proteins; Cell Communication; Cell Movement; Chemoreceptor Cells; Chemotaxis; Membrane Proteins; Signal Transduction; Vibrio parahaemolyticus
PubMed: 30938898
DOI: 10.1111/mmi.14256 -
Cell Metabolism Apr 2012Food intake is detected by the chemical senses of taste and smell and subsequently by chemosensory cells in the gastrointestinal tract that link the composition of... (Review)
Review
Food intake is detected by the chemical senses of taste and smell and subsequently by chemosensory cells in the gastrointestinal tract that link the composition of ingested foods to feedback circuits controlling gut motility/secretion, appetite, and peripheral nutrient disposal. G-protein-coupled receptors responsive to a range of nutrients and other food components have been identified, and many are localized to intestinal chemosensory cells, eliciting hormonal and neuronal signaling to the brain and periphery. This review examines the role of G-protein-coupled receptors as signaling molecules in the gut, with a particular focus on pathways relevant to appetite and glucose homeostasis.
Topics: Animals; Cannabinoid Receptor Modulators; Chemoreceptor Cells; Humans; Intestinal Mucosa; Neurotransmitter Agents; Receptors, G-Protein-Coupled; Signal Transduction
PubMed: 22482725
DOI: 10.1016/j.cmet.2011.12.019 -
Cellular and Molecular Life Sciences :... Jul 2006Taste bud cells communicate with sensory afferent fibers and may also exchange information with adjacent cells. Indeed, communication between taste cells via... (Review)
Review
Taste bud cells communicate with sensory afferent fibers and may also exchange information with adjacent cells. Indeed, communication between taste cells via conventional and/or novel synaptic interactions may occur prior to signal output to primary afferent fibers. This review discusses synaptic processing in taste buds and summarizes results showing that it is now possible to measure real-time release of synaptic transmitters during taste stimulation using cellular biosensors. There is strong evidence that serotonin and ATP play a role in cell-to-cell signaling and sensory output in the gustatory end organs.
Topics: Adenosine Triphosphate; Animals; Cell Communication; Chemoreceptor Cells; Forecasting; Humans; Neurotransmitter Agents; Receptors, Serotonin; Serotonin; Signal Transduction; Taste Buds
PubMed: 16732426
DOI: 10.1007/s00018-006-6112-9 -
Pflugers Archiv : European Journal of... Nov 2021Chemosensory processes are integral to the physiology of most organisms. This function is typically performed by specialized cells that are able to detect input signals... (Review)
Review
Chemosensory processes are integral to the physiology of most organisms. This function is typically performed by specialized cells that are able to detect input signals and to convert them to an output dedicated to a particular group of target cells. Tuft cells are cholinergic chemosensory epithelial cells capable of producing immunologically relevant effector molecules. They are scattered throughout endoderm-derived hollow organs and function as sensors of luminal stimuli, which has been best studied in mucosal barrier epithelia. Given their epithelial origin and broad distribution, and based on their interplay with immune pathways, tuft cells can be considered a prototypical example of how complex multicellular organisms engage innate immune mechanisms to modulate and optimize organ physiology. In this review, I provide a concise overview of tuft cells and discuss how these cells influence organ adaptation to dynamic luminal conditions.
Topics: Animals; Chemoreceptor Cells; Epithelial Cells; Humans; Immunity, Innate
PubMed: 34635955
DOI: 10.1007/s00424-021-02630-2