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Dutta Banik D, Medler KF. Bitter, sweet, and umami signaling in taste cells: it’s not as simple as we thought. CURRENT OPINION IN PHYSIOLOGY 2021. [DOI: 10.1016/j.cophys.2021.01.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Abstract
All organisms have the ability to detect chemicals in the environment, which likely evolved out of organisms' needs to detect food sources and avoid potentially harmful compounds. The taste system detects chemicals and is used to determine whether potential food items will be ingested or rejected. The sense of taste detects five known taste qualities: bitter, sweet, salty, sour, and umami, which is the detection of amino acids, specifically glutamate. These different taste qualities encompass a wide variety of chemicals that differ in their structure and as a result, the peripheral taste utilizes numerous and diverse mechanisms to detect these stimuli. In this chapter, we will summarize what is currently known about the signaling mechanisms used by taste cells to transduce stimulus signals.
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Affiliation(s)
- Debarghya Dutta Banik
- Department of Biological Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, NY, USA
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kathryn F Medler
- Department of Biological Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, NY, USA.
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Dutta Banik D, Benfey ED, Martin LE, Kay KE, Loney GC, Nelson AR, Ahart ZC, Kemp BT, Kemp BR, Torregrossa AM, Medler KF. A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli. PLoS Genet 2020; 16:e1008925. [PMID: 32790785 PMCID: PMC7425866 DOI: 10.1371/journal.pgen.1008925] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 06/10/2020] [Indexed: 12/20/2022] Open
Abstract
Taste receptor cells use multiple signaling pathways to detect chemicals in potential food items. These cells are functionally grouped into different types: Type I cells act as support cells and have glial-like properties; Type II cells detect bitter, sweet, and umami taste stimuli; and Type III cells detect sour and salty stimuli. We have identified a new population of taste cells that are broadly tuned to multiple taste stimuli including bitter, sweet, sour, and umami. The goal of this study was to characterize these broadly responsive (BR) taste cells. We used an IP3R3-KO mouse (does not release calcium (Ca2+) from internal stores in Type II cells when stimulated with bitter, sweet, or umami stimuli) to characterize the BR cells without any potentially confounding input from Type II cells. Using live cell Ca2+ imaging in isolated taste cells from the IP3R3-KO mouse, we found that BR cells are a subset of Type III cells that respond to sour stimuli but also use a PLCβ signaling pathway to respond to bitter, sweet, and umami stimuli. Unlike Type II cells, individual BR cells are broadly tuned and respond to multiple stimuli across different taste modalities. Live cell imaging in a PLCβ3-KO mouse confirmed that BR cells use this signaling pathway to respond to bitter, sweet, and umami stimuli. Short term behavioral assays revealed that BR cells make significant contributions to taste driven behaviors and found that loss of either PLCβ3 in BR cells or IP3R3 in Type II cells caused similar behavioral deficits to bitter, sweet, and umami stimuli. Analysis of c-Fos activity in the nucleus of the solitary tract (NTS) also demonstrated that functional Type II and BR cells are required for normal stimulus induced expression. We use our taste system to decide if we are going to consume or reject a potential food item. This is critical for survival, as we need energy to live but also need to avoid potentially toxic compounds. Therefore, it is important to understand how the taste cells in our mouth detect the chemicals in food and send a message to our brain. Signals from the taste cells form a code that conveys information about the nature of the potential food item to the brain. How this taste coding works is not well understood. Currently, it is thought that taste cells are primarily selective for each taste stimuli and only detect either bitter, sweet, sour, salt, or umami (amino acids) compounds. Our study describes a new population of taste cells that can detect multiple types of stimuli, including chemicals from different taste qualities. Thus, taste cells can be either selective or generally responsive to stimuli which is similar to the cells in the brain that process taste information. The presence of these broadly responsive taste cells provides new insight into how taste information is sent to the brain for processing.
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Affiliation(s)
- Debarghya Dutta Banik
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Eric D. Benfey
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Laura E. Martin
- Department of Psychology, University at Buffalo, Buffalo, New York, United States of America
| | - Kristen E. Kay
- Department of Psychology, University at Buffalo, Buffalo, New York, United States of America
| | - Gregory C. Loney
- Department of Psychology, University at Buffalo, Buffalo, New York, United States of America
| | - Amy R. Nelson
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Zachary C. Ahart
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Barrett T. Kemp
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Bailey R. Kemp
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
| | - Ann-Marie Torregrossa
- Department of Psychology, University at Buffalo, Buffalo, New York, United States of America
- Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York, United States of America
| | - Kathryn F. Medler
- Department of Biological Sciences, University at Buffalo, Buffalo, New York, United States of America
- Center for Ingestive Behavior Research, University at Buffalo, Buffalo, New York, United States of America
- * E-mail:
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Mouillot T, Barthet S, Janin L, Creteau C, Devilliers H, Brindisi MC, Penicaud L, Leloup C, Brondel L, Jacquin-Piques A. Taste Perception and Cerebral Activity in the Human Gustatory Cortex Induced by Glucose, Fructose, and Sucrose Solutions. Chem Senses 2019; 44:435-447. [PMID: 31168584 DOI: 10.1093/chemse/bjz034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Glucose, fructose, and sucrose are important carbohydrates in Western diets with particular sweetness intensity and metabolisms. No study has compared their cerebral detection and their taste perception. Gustatory evoked potentials (GEPs), taste detection thresholds, intensity perception, and pleasantness were compared in response to glucose, fructose, and sucrose solutions at similar sweetness intensities and at identical molar concentrations. Twenty-three healthy subjects were randomly stimulated with 3 solutions of similar sweetness intensity (0.75 M of glucose, 0.47 M of fructose and 0.29 M of sucrose - sit. A), and with an identical molar concentration (0.29 M - sit. B). GEPs were recorded at gustatory cortex areas. Intensity perception and hedonic values of each solution were evaluated as were gustatory thresholds of the solutions. No significant difference was observed concerning the GEP characteristics of the solutions according to their sweetness intensities (sit. A) or their molar concentration (sit. B). In sit. A, the 3 solutions were perceived to have similar intensities and induced similar hedonic sensations. In sit. B, the glucose solution was perceived to be less intense and pleasant than the fructose and the sucrose solutions (P < 0.001) and the fructose solution was perceived to be less intense and pleasant than the sucrose (P < 0.001). Since GEP recordings were similar for glucose, fructose, and sucrose solutions whatever the concentrations, activation of same taste receptor induces similar cortical activation, even when the solutions were perceived differently. Sweet taste perception seems to be encoded by a complex chemical cerebral neuronal network.
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Affiliation(s)
- Thomas Mouillot
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France.,CHU Dijon - Bourgogne - Department of Hepatology and Gastroenterology, Rue Paul Gaffarel, Dijon, France
| | - Sophie Barthet
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France
| | - Lucie Janin
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France
| | - Camille Creteau
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France
| | - Hervé Devilliers
- CHU Dijon - Bourgogne - CIC-EC INSERM, Rue Paul Gaffarel, Dijon, France
| | - Marie-Claude Brindisi
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France.,CHU Dijon - Bourgogne - Department of Hepatology and Gastroenterology, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - CIC-EC INSERM, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - Department of Endocrinology and Nutrition, Rue Paul Gaffarel, Dijon, France
| | - Luc Penicaud
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France.,CHU Dijon - Bourgogne - Department of Hepatology and Gastroenterology, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - CIC-EC INSERM, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - Department of Endocrinology and Nutrition, Rue Paul Gaffarel, Dijon, France
| | - Corinne Leloup
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France
| | - Laurent Brondel
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France.,CHU Dijon - Bourgogne - Department of Hepatology and Gastroenterology, Rue Paul Gaffarel, Dijon, France
| | - Agnès Jacquin-Piques
- Centre des Sciences du goût et de l'Alimentation, AgroSup Dijon, CNRS, INRA, Université Bourgogne Franche-Comté, Dijon, France.,CHU Dijon - Bourgogne - Department of Hepatology and Gastroenterology, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - CIC-EC INSERM, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - Department of Endocrinology and Nutrition, Rue Paul Gaffarel, Dijon, France.,CHU Dijon - Bourgogne - Department of Clinical Neurophysiology, Rue Paul Gaffarel, Dijon, France
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A light-addressable microfluidic device for label-free functional assays of bioengineered taste receptor cells via extracellular recording. BIOPHYSICS REPORTS 2019. [DOI: 10.1007/s41048-019-0085-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
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6
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Schier LA, Spector AC. The Functional and Neurobiological Properties of Bad Taste. Physiol Rev 2019; 99:605-663. [PMID: 30475657 PMCID: PMC6442928 DOI: 10.1152/physrev.00044.2017] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 05/18/2018] [Accepted: 06/30/2018] [Indexed: 12/12/2022] Open
Abstract
The gustatory system serves as a critical line of defense against ingesting harmful substances. Technological advances have fostered the characterization of peripheral receptors and have created opportunities for more selective manipulations of the nervous system, yet the neurobiological mechanisms underlying taste-based avoidance and aversion remain poorly understood. One conceptual obstacle stems from a lack of recognition that taste signals subserve several behavioral and physiological functions which likely engage partially segregated neural circuits. Moreover, although the gustatory system evolved to respond expediently to broad classes of biologically relevant chemicals, innate repertoires are often not in register with the actual consequences of a food. The mammalian brain exhibits tremendous flexibility; responses to taste can be modified in a specific manner according to bodily needs and the learned consequences of ingestion. Therefore, experimental strategies that distinguish between the functional properties of various taste-guided behaviors and link them to specific neural circuits need to be applied. Given the close relationship between the gustatory and visceroceptive systems, a full reckoning of the neural architecture of bad taste requires an understanding of how these respective sensory signals are integrated in the brain.
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Affiliation(s)
- Lindsey A Schier
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Alan C Spector
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
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Boudjarane MA, Grandgeorge M, Marianowski R, Misery L, Lemonnier É. Perception of odors and tastes in autism spectrum disorders: A systematic review of assessments. Autism Res 2017; 10:1045-1057. [PMID: 28371114 DOI: 10.1002/aur.1760] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 01/09/2017] [Accepted: 01/13/2017] [Indexed: 11/11/2022]
Abstract
Olfaction and gustation are major sensory functions implied in processing environmental stimuli. Some evidences suggest that loss of olfactory function is an early biomarker for neurodegenerative disorders and atypical processing of odor and taste stimuli is present in several neurodevelopmental disorders, notably in Autism Spectrum Disorders (ASD). In this paper, we conducted a systematic review investigating the assessments of olfaction and gustation with psychophysics methods in individuals with ASD. Pubmed, PMC and Sciencedirect were scrutinized for relevant literature published from 1970 to 2015. In this review, fourteen papers met our inclusion criteria. They were analyzed critically in order to evaluate the occurrence of olfactory and gustatory dysfunction in ASD, as well as to report the methods used to assess olfaction and gustation in such conditions. Regarding to these two senses, the overall number of studies is low. Most of studies show significant difference regarding to odor or taste identification but not for detection threshold. Overall, odor rating through pleasantness, intensity and familiarity do not differ significantly between control and individuals with ASD. The current evidences can suggest the presence of olfactory and gustatory dysfunction in ASD. Therefore, our analysis show a heterogeneity of findings. This is due to several methodological limitations such as the tools used or population studied. Understanding these disorders could help to shed light on other atypical behavior in this population such as feeding or social behavior. Autism Res 2017, 0: 000-000. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. Autism Res 2017, 10: 1045-1057. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.
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Affiliation(s)
- Mohamed A Boudjarane
- Laboratory of Neurosciences of Brest (EA4685), University of Western Brittany, Brest, France
| | - Marine Grandgeorge
- Laboratory of Neurosciences of Brest (EA4685), University of Western Brittany, Brest, France.,UMR-CNRS 6552, Animal and Human Ethology University of Rennes 1-CNRS, Rennes Cedex, France
| | - Rémi Marianowski
- Laboratory of Neurosciences of Brest (EA4685), University of Western Brittany, Brest, France.,Department of ENT, University Hospital of Brest, Brest Cedex, France
| | - Laurent Misery
- Laboratory of Neurosciences of Brest (EA4685), University of Western Brittany, Brest, France.,Department of Dermatology, University Hospital of Brest, Brest Cedex, France
| | - Éric Lemonnier
- Laboratory of Neurosciences of Brest (EA4685), University of Western Brittany, Brest, France.,University Hospital of Limoges, Expert Center of Autism Limousin, Limoges Cedex, France (É.L.)
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8
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Lu L, Hu X, Zhu Z. Biomimetic sensors and biosensors for qualitative and quantitative analyses of five basic tastes. Trends Analyt Chem 2017. [DOI: 10.1016/j.trac.2016.12.007] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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9
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Chemosensory epithelial cells in the urethra: sentinels of the urinary tract. Histochem Cell Biol 2016; 146:673-683. [PMID: 27680547 DOI: 10.1007/s00418-016-1504-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/21/2016] [Indexed: 12/27/2022]
Abstract
A peculiar cell type of the respiratory and gastrointestinal epithelia, originally termed "brush cell" or "tuft cell" by electron microscopists because of its apical tuft of microvilli, utilizes the canonical bitter taste transduction cascade known from oropharyngeal taste buds to detect potential hazardous compounds, e.g. bacterial products. Upon stimulation, this cell initiates protective reflexes and local inflammatory responses through release of acetylcholine and chemokines. Guided by the understanding of these cells as sentinels, they have been newly discovered at previously unrecognized anatomical locations, including the urethra. Solitary cholinergic urethral cells express canonical taste receptors and are polymodal chemosensors for certain bitter substances, glutamate (umami) and uropathogenic Escherichia coli. Intraurethral bitter stimulation triggers cholinergic reflex activation of bladder detrusor activity, which is interpreted as cleaning flushing of the urethra. The currently known scenario suggests the presence of at least two more urethral chemosensory cell types: non-cholinergic brush cells and neuroendocrine serotonergic cells. The potential implications are enormous and far reaching, as these cells might be involved in monitoring and preventing ascending urinary tract infection and triggering of inappropriate detrusor activity. However, although appealing, this is still highly speculative, since the actual number of distinct chemosensory cell types needs to be finally clarified, as well as their embryological origin, developmental dynamics, receptor equipment, modes of signalling to adjacent nerve fibres and other cells, repertoire of chemo- and cytokines, involvement in pathogenesis of diseases and many other aspects.
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Wu C, Lillehoj PB, Wang P. Bioanalytical and chemical sensors using living taste, olfactory, and neural cells and tissues: a short review. Analyst 2016; 140:7048-61. [PMID: 26308143 DOI: 10.1039/c5an01288k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Biosensors utilizing living tissues and cells have recently gained significant attention as functional devices for chemical sensing and biochemical analysis. These devices integrate biological components (i.e. single cells, cell networks, tissues) with micro-electro-mechanical systems (MEMS)-based sensors and transducers. Various types of cells and tissues derived from natural and bioengineered sources have been used as recognition and sensing elements, which are generally characterized by high sensitivity and specificity. This review summarizes the state of the art in tissue- and cell-based biosensing platforms with an emphasis on those using taste, olfactory, and neural cells and tissues. Many of these devices employ unique integration strategies and sensing schemes based on sensitive transducers including microelectrode arrays (MEAs), field effect transistors (FETs), and light-addressable potentiometric sensors (LAPSs). Several groups have coupled these hybrid biosensors with microfluidics which offers added benefits of small sample volumes and enhanced automation. While this technology is currently limited to lab settings due to the limited stability of living biological components, further research to enhance their robustness will enable these devices to be employed in field and clinical settings.
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Affiliation(s)
- Chunsheng Wu
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Ministry of Education, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
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A novel bioelectronic tongue in vivo for highly sensitive bitterness detection with brain–machine interface. Biosens Bioelectron 2016; 78:374-380. [DOI: 10.1016/j.bios.2015.11.078] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/24/2015] [Accepted: 11/26/2015] [Indexed: 11/22/2022]
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Breadth of tuning in taste afferent neurons varies with stimulus strength. Nat Commun 2015; 6:8171. [PMID: 26373451 PMCID: PMC4573454 DOI: 10.1038/ncomms9171] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 07/27/2015] [Indexed: 12/20/2022] Open
Abstract
Gustatory stimuli are detected by taste buds and transmitted to the hindbrain via sensory afferent neurons. Whether each taste quality (sweet, bitter and so on) is encoded by separate neurons (‘labelled lines') remains controversial. We used mice expressing GCaMP3 in geniculate ganglion sensory neurons to investigate taste-evoked activity. Using confocal calcium imaging, we recorded responses to oral stimulation with prototypic taste stimuli. Up to 69% of neurons respond to multiple tastants. Moreover, neurons tuned to a single taste quality at low concentration become more broadly tuned when stimuli are presented at higher concentration. Responses to sucrose and monosodium glutamate are most related. Although mice prefer dilute NaCl solutions and avoid concentrated NaCl, we found no evidence for two separate populations of sensory neurons that encode this distinction. Altogether, our data suggest that taste is encoded by activity in patterns of peripheral sensory neurons and challenge the notion of strict labelled line coding. How taste information is encoded and transmitted from the periphery to the cortex is not well understood. Here the authors provide evidence for population-based coding of taste by demonstrating that more than half of individual geniculate ganglion neurons are broadly tuned to basic taste stimuli.
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Pal Choudhuri S, Delay RJ, Delay ER. L-Amino Acids Elicit Diverse Response Patterns in Taste Sensory Cells: A Role for Multiple Receptors. PLoS One 2015; 10:e0130088. [PMID: 26110622 PMCID: PMC4482487 DOI: 10.1371/journal.pone.0130088] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 05/15/2015] [Indexed: 12/01/2022] Open
Abstract
Umami, the fifth basic taste, is elicited by the L-amino acid, glutamate. A unique characteristic of umami taste is the response potentiation by 5’ ribonucleotide monophosphates, which are also capable of eliciting an umami taste. Initial reports using human embryonic kidney (HEK) cells suggested that there is one broadly tuned receptor heterodimer, T1r1+T1r3, which detects L-glutamate and all other L-amino acids. However, there is growing evidence that multiple receptors detect glutamate in the oral cavity. While much is understood about glutamate transduction, the mechanisms for detecting the tastes of other L-amino acids are less well understood. We used calcium imaging of isolated taste sensory cells and taste cell clusters from the circumvallate and foliate papillae of C57BL/6J and T1r3 knockout mice to determine if other receptors might also be involved in detection of L-amino acids. Ratiometric imaging with Fura-2 was used to study calcium responses to monopotassium L-glutamate, L-serine, L-arginine, and L-glutamine, with and without inosine 5’ monophosphate (IMP). The results of these experiments showed that the response patterns elicited by L-amino acids varied significantly across taste sensory cells. L-amino acids other than glutamate also elicited synergistic responses in a subset of taste sensory cells. Along with its role in synergism, IMP alone elicited a response in a large number of taste sensory cells. Our data indicate that synergistic and non-synergistic responses to L-amino acids and IMP are mediated by multiple receptors or possibly a receptor complex.
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Affiliation(s)
- Shreoshi Pal Choudhuri
- Department of Biology and Vermont Chemosensory Group, The University of Vermont, Burlington, Vermont, United States of America
| | - Rona J. Delay
- Department of Biology and Vermont Chemosensory Group, The University of Vermont, Burlington, Vermont, United States of America
| | - Eugene R. Delay
- Department of Biology and Vermont Chemosensory Group, The University of Vermont, Burlington, Vermont, United States of America
- * E-mail:
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Sharma RK, Duda T. Membrane guanylate cyclase, a multimodal transduction machine: history, present, and future directions. Front Mol Neurosci 2014; 7:56. [PMID: 25071437 PMCID: PMC4079103 DOI: 10.3389/fnmol.2014.00056] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 05/30/2014] [Indexed: 12/22/2022] Open
Abstract
A sequel to these authors' earlier comprehensive reviews which covered the field of mammalian membrane guanylate cyclase (MGC) from its origin to the year 2010, this article contains 13 sections. The first is historical and covers MGC from the year 1963–1987, summarizing its colorful developmental stages from its passionate pursuit to its consolidation. The second deals with the establishment of its biochemical identity. MGC becomes the transducer of a hormonal signal and founder of the peptide hormone receptor family, and creates the notion that hormone signal transduction is its sole physiological function. The third defines its expansion. The discovery of ROS-GC subfamily is made and it links ROS-GC with the physiology of phototransduction. Sections ROS-GC, a Ca2+-Modulated Two Component Transduction System to Migration Patterns and Translations of the GCAP Signals Into Production of Cyclic GMP are Different cover its biochemistry and physiology. The noteworthy events are that augmented by GCAPs, ROS-GC proves to be a transducer of the free Ca2+ signals generated within neurons; ROS-GC becomes a two-component transduction system and establishes itself as a source of cyclic GMP, the second messenger of phototransduction. Section ROS-GC1 Gene Linked Retinal Dystrophies demonstrates how this knowledge begins to be translated into the diagnosis and providing the molecular definition of retinal dystrophies. Section Controlled By Low and High Levels of [Ca2+]i, ROS-GC1 is a Bimodal Transduction Switch discusses a striking property of ROS-GC where it becomes a “[Ca2+]i bimodal switch” and transcends its signaling role in other neural processes. In this course, discovery of the first CD-GCAP (Ca2+-dependent guanylate cyclase activator), the S100B protein, is made. It extends the role of the ROS-GC transduction system beyond the phototransduction to the signaling processes in the synapse region between photoreceptor and cone ON-bipolar cells; in section Ca2+-Modulated Neurocalcin δ ROS-GC1 Transduction System Exists in the Inner Plexiform Layer (IPL) of the Retinal Neurons, discovery of another CD-GCAP, NCδ, is made and its linkage with signaling of the inner plexiform layer neurons is established. Section ROS-GC Linkage With Other Than Vision-Linked Neurons discusses linkage of the ROS-GC transduction system with other sensory transduction processes: Pineal gland, Olfaction and Gustation. In the next, section Evolution of a General Ca2+-Interlocked ROS-GC Signal Transduction Concept in Sensory and Sensory-Linked Neurons, a theoretical concept is proposed where “Ca2+-interlocked ROS-GC signal transduction” machinery becomes a common signaling component of the sensory and sensory-linked neurons. Closure to the review is brought by the conclusion and future directions.
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Affiliation(s)
- Rameshwar K Sharma
- Research Divisions of Biochemistry and Molecular Biology, The Unit of Regulatory and Molecular Biology, Salus University Elkins Park, PA, USA
| | - Teresa Duda
- Research Divisions of Biochemistry and Molecular Biology, The Unit of Regulatory and Molecular Biology, Salus University Elkins Park, PA, USA
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Sekine H, Takao K, Yoshinaga K, Kokubun S, Ikeda M. Effects of zinc deficiency and supplementation on gene expression of bitter taste receptors (TAS2Rs) on the tongue in rats. Laryngoscope 2012; 122:2411-7. [DOI: 10.1002/lary.23378] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/27/2012] [Accepted: 03/30/2012] [Indexed: 11/10/2022]
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16
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Ferrer RP, Zimmer RK. Community ecology and the evolution of molecules of keystone significance. THE BIOLOGICAL BULLETIN 2012; 223:167-177. [PMID: 23111129 DOI: 10.1086/bblv223n2p167] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Molecules of keystone significance are vital in structuring ecological communities. Select bioactive compounds can cause disproportionately large effects by connecting such seemingly disparate processes as microbial loop dynamics and apex predation. Here, we develop a general theory and propose mechanisms that could lead to the evolution of keystone molecules. Introduced into a respective community by one, or only a few, autotrophic or microbial species, these compounds often originate as chemical defenses. When co-opted by resistant consumer species, however, they are used either in chemical defense against higher-order predators or as chemosensory cues that elicit courtship and mating, alarm, and predatory search. Requisite to these multifunctional properties, biosynthetic capacity evolves along with mechanisms for resistance and/or toxin storage in primary producers. Subsequently, consumers acquire resistances or tolerances, and the toxins are transferred through food webs via trophic interactions. In consumers, mechanisms eventually evolve for recognizing toxins as feeding cues and, ultimately, as signals or pheromones in chemical communication within or between species. One, or a few, active compounds can thus mediate a vast array of physiological traits, expressed differentially across many species in a given community. Through convergent evolution, molecules of keystone significance provide critical information to phylogenetically diverse species, initiate major trophic cascades, and structure communities within terrestrial, freshwater, coastal-ocean and open-ocean habitats.
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Affiliation(s)
- Ryan P Ferrer
- Department of Biology, Seattle Pacific University, 3307 Third Avenue West, Seattle, Washington 98119, USA.
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17
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Abstract
The taste system is one of our fundamental senses, responsible for detecting and responding to sweet, bitter, umami, salty, and sour stimuli. In the tongue, the five basic tastes are mediated by separate classes of taste receptor cells each finely tuned to a single taste quality. We explored the logic of taste coding in the brain by examining how sweet, bitter, umami, and salty qualities are represented in the primary taste cortex of mice. We used in vivo two-photon calcium imaging to demonstrate topographic segregation in the functional architecture of the gustatory cortex. Each taste quality is represented in its own separate cortical field, revealing the existence of a gustotopic map in the brain. These results expose the basic logic for the central representation of taste.
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Affiliation(s)
- Xiaoke Chen
- Howard Hughes Medical Institute and Departments of Biochemistry and Molecular Biophysics and of Neuroscience, Columbia College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | - Mariano Gabito
- Howard Hughes Medical Institute and Departments of Biochemistry and Molecular Biophysics and of Neuroscience, Columbia College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | - Yueqing Peng
- Howard Hughes Medical Institute and Departments of Biochemistry and Molecular Biophysics and of Neuroscience, Columbia College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
| | - Nicholas J.P. Ryba
- National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Charles S. Zuker
- Howard Hughes Medical Institute and Departments of Biochemistry and Molecular Biophysics and of Neuroscience, Columbia College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
- Departments of Neurobiology and Neurosciences, University of California at San Diego, La Jolla, California 92093-0649, USA
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Treesukosol Y, Mathes CM, Spector AC. Citric acid and quinine share perceived chemosensory features making oral discrimination difficult in C57BL/6J mice. Chem Senses 2011; 36:477-89. [PMID: 21421543 DOI: 10.1093/chemse/bjr010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Evidence in the literature shows that in rodents, some taste-responsive neurons respond to both quinine and acid stimuli. Also, under certain circumstances, rodents display some degree of difficulty in discriminating quinine and acid stimuli. Here, C57BL/6J mice were trained and tested in a 2-response operant discrimination task. Mice had severe difficulty discriminating citric acid from quinine and 6-n-propylthiouracil (PROP) with performance slightly, but significantly, above chance. In contrast, mice were able to competently discriminate sucrose from citric acid, NaCl, quinine, and PROP. In another experiment, mice that were conditioned to avoid quinine by pairings with LiCl injections subsequently suppressed licking responses to quinine and citric acid but not to NaCl or sucrose in a brief-access test, relative to NaCl-injected control animals. However, mice that were conditioned to avoid citric acid did not display cross-generalization to quinine. These mice significantly suppressed licking only to citric acid, and to a much lesser extent NaCl, compared with controls. Collectively, the findings from these experiments suggest that in mice, citric acid and quinine share chemosensory features making discrimination difficult but are not perceptually identical.
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Affiliation(s)
- Yada Treesukosol
- Department of Psychology, Program in Neuroscience, Florida State University, Tallahassee, FL 32306-4301, USA
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19
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Abstract
Taste buds are aggregates of 50–100 polarized neuroepithelial cells that detect nutrients and other compounds. Combined analyses of gene expression and cellular function reveal an elegant cellular organization within the taste bud. This review discusses the functional classes of taste cells, their cell biology, and current thinking on how taste information is transmitted to the brain.
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Affiliation(s)
- Nirupa Chaudhari
- Department of Physiology and Biophysics, and Program in Neurosciences, University of Miami Miller School of Medicine, Miami, FL 33136, USA.
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20
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Huang YA, Roper SD. Intracellular Ca(2+) and TRPM5-mediated membrane depolarization produce ATP secretion from taste receptor cells. J Physiol 2010; 588:2343-50. [PMID: 20498227 DOI: 10.1113/jphysiol.2010.191106] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
ATP is a transmitter secreted from taste bud receptor (Type II) cells through ATP-permeable gap junction hemichannels most probably composed of pannexin 1. The elevation of intracellular Ca(2+) and membrane depolarization are both believed to be involved in transmitter secretion from receptor cells, but their specific roles have not been fully elucidated. In the present study, we show that taste-evoked ATP secretion from mouse vallate receptor cells is evoked by the combination of intracellular Ca(2+) release and membrane depolarization. Unexpectedly, ATP secretion is not blocked by tetrodotoxin, indicating that transmitter release from these cells still takes place in the absence of action potentials. Taste-evoked ATP secretion is absent in receptor cells isolated from TRPM5 knockout mice or in taste cells from wild type mice where current through TRPM5 channels has been eliminated. These findings suggest that membrane voltage initiated by TRPM5 channels is required for ATP secretion during taste reception. Nonetheless, even in the absence of TRPM5 channel activity, ATP release could be triggered by depolarizing cells with KCl. Collectively, the findings indicate that taste-evoked elevation of intracellular Ca(2+) has a dual role: (1) Ca(2+) opens TRPM5 channels to depolarize receptor cells and (2) Ca(2+) plus membrane depolarization opens ATP-permeable gap junction hemichannels.
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Affiliation(s)
- Yijen A Huang
- Department of Physiology and Biophysics, University of Miami School of Medicine, Miami, FL 33136, USA
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21
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Carleton A, Accolla R, Simon SA. Coding in the mammalian gustatory system. Trends Neurosci 2010; 33:326-34. [PMID: 20493563 DOI: 10.1016/j.tins.2010.04.002] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2007] [Revised: 03/29/2010] [Accepted: 04/13/2010] [Indexed: 01/17/2023]
Abstract
To understand gustatory physiology and associated dysfunctions it is important to know how oral taste stimuli are encoded both in the periphery and in taste-related brain centres. The identification of distinct taste receptors, together with electrophysiological recordings and behavioral assessments in response to taste stimuli, suggest that information about distinct taste modalities (e.g. sweet versus bitter) are transmitted from the periphery to the brain via segregated pathways. By contrast, gustatory neurons throughout the brain are more broadly tuned, indicating that ensembles of neurons encode taste qualities. Recent evidence reviewed here suggests that the coding of gustatory stimuli is not immutable, but is dependant on a variety of factors including appetite-regulating molecules and associative learning.
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Affiliation(s)
- Alan Carleton
- Department of Neurosciences, Medical Faculty, University of Geneva, 1 rue Michel-Servet, 1211 Genève 4, Switzerland.
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22
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Yoshida R, Ninomiya Y. New Insights into the Signal Transmission from Taste Cells to Gustatory Nerve Fibers. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2010; 279:101-34. [DOI: 10.1016/s1937-6448(10)79004-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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23
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ROS-GC subfamily membrane guanylate cyclase-linked transduction systems: taste, pineal gland and hippocampus. Mol Cell Biochem 2009; 334:199-206. [PMID: 19953306 DOI: 10.1007/s11010-009-0334-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Accepted: 11/04/2009] [Indexed: 10/20/2022]
Abstract
In the continuous efforts to test the validity of the theme that the Ca(2+)-modulated ROS-GC subfamily system is a universal transduction component of the sensory and sensory-linked network of neurons, this article focuses on the presence and variant biochemical forms of this transduction system in the gustatory epithelium, the site of gustatory transduction; in the pineal, a light-sensitive gland; and in the hippocampus neurons, linked with the perception of all SENSES.
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24
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Gilbertson T, Yu T, Shah B. Gustatory Mechanisms for Fat Detection. Front Neurosci 2009. [DOI: 10.1201/9781420067767-c3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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25
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Sweet, bitter and umami receptors: a complex relationship. Trends Biochem Sci 2009; 34:296-302. [DOI: 10.1016/j.tibs.2009.02.005] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 02/13/2009] [Accepted: 02/18/2009] [Indexed: 11/18/2022]
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26
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The neuropeptides CCK and NPY and the changing view of cell-to-cell communication in the taste bud. Physiol Behav 2009; 97:581-91. [PMID: 19332083 DOI: 10.1016/j.physbeh.2009.02.043] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Accepted: 02/16/2009] [Indexed: 11/24/2022]
Abstract
The evolving view of the taste bud increasingly suggests that it operates as a complex signal processing unit. A number of neurotransmitters and neuropeptides and their corresponding receptors are now known to be expressed in subsets of taste receptor cells in the mammalian bud. These expression patterns set up hard-wired cell-to-cell communication pathways whose exact physiological roles still remain obscure. As occurs in other cellular systems, it is likely that neuropeptides are co-expressed with neurotransmitters and function as neuromodulators. Several neuropeptides have been identified in taste receptor cells including cholecystokinin (CCK), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), and glucagon-like peptide 1 (GLP-1). Of these, CCK and NPY are the best studied. These two peptides are co-expressed in the same presynaptic cells; however, their postsynaptic actions are both divergent and antagonistic. CCK and its receptor, the CCK-1 subtype, are expressed in the same subset of taste receptor cells and the autocrine activation of these cells produces a number of excitatory physiological actions. Further, most of these cells are responsive to bitter stimuli. On the other hand, NPY and its receptor, the NPY-1 subtype, are expressed in different cells. NPY, acting in a paracrine fashion on NPY-1 receptors, results in inhibitory actions on the cell. Preliminary evidence suggests the NPY-1 receptor expressing cell co-expresses T1R3, a member of the T1R family of G-protein coupled receptors thought to be important in detection of sweet and umami stimuli. Thus the neuropeptide expressing cells co-express CCK, NPY, and CCK-1 receptor. Neuropeptides released from these cells during bitter stimulation may work in concert to both modulate the excitation of bitter-sensitive taste receptor cells while concurrently inhibiting sweet-sensitive cells. This modulatory process is similar to the phenomenon of lateral inhibition that occurs in other sensory systems.
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27
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Gao N, Lu M, Echeverri F, Laita B, Kalabat D, Williams ME, Hevezi P, Zlotnik A, Moyer BD. Voltage-gated sodium channels in taste bud cells. BMC Neurosci 2009; 10:20. [PMID: 19284629 PMCID: PMC2660338 DOI: 10.1186/1471-2202-10-20] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2008] [Accepted: 03/12/2009] [Indexed: 12/19/2022] Open
Abstract
Background Taste bud cells transmit information regarding the contents of food from taste receptors embedded in apical microvilli to gustatory nerve fibers innervating basolateral membranes. In particular, taste cells depolarize, activate voltage-gated sodium channels, and fire action potentials in response to tastants. Initial cell depolarization is attributable to sodium influx through TRPM5 in sweet, bitter, and umami cells and an undetermined cation influx through an ion channel in sour cells expressing PKD2L1, a candidate sour taste receptor. The molecular identity of the voltage-gated sodium channels that sense depolarizing signals and subsequently initiate action potentials coding taste information to gustatory nerve fibers is unknown. Results We describe the molecular and histological expression profiles of cation channels involved in electrical signal transmission from apical to basolateral membrane domains. TRPM5 was positioned immediately beneath tight junctions to receive calcium signals originating from sweet, bitter, and umami receptor activation, while PKD2L1 was positioned at the taste pore. Using mouse taste bud and lingual epithelial cells collected by laser capture microdissection, SCN2A, SCN3A, and SCN9A voltage-gated sodium channel transcripts were expressed in taste tissue. SCN2A, SCN3A, and SCN9A were expressed beneath tight junctions in subsets of taste cells. SCN3A and SCN9A were expressed in TRPM5 cells, while SCN2A was expressed in TRPM5 and PKD2L1 cells. HCN4, a gene previously implicated in sour taste, was expressed in PKD2L1 cells and localized to cell processes beneath the taste pore. Conclusion SCN2A, SCN3A and SCN9A voltage-gated sodium channels are positioned to sense initial depolarizing signals stemming from taste receptor activation and initiate taste cell action potentials. SCN2A, SCN3A and SCN9A gene products likely account for the tetrodotoxin-sensitive sodium currents in taste receptor cells.
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Affiliation(s)
- Na Gao
- Senomyx, Inc, 4767 Nexus Centre Drive, San Diego, CA 92121, USA.
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28
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Roberts CD, Dvoryanchikov G, Roper SD, Chaudhari N. Interaction between the second messengers cAMP and Ca2+ in mouse presynaptic taste cells. J Physiol 2009; 587:1657-68. [PMID: 19221121 DOI: 10.1113/jphysiol.2009.170555] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
The second messenger, 3',5'-cyclic adenosine monophosphate (cAMP), is known to be modulated in taste buds following exposure to gustatory and other stimuli. Which taste cell type(s) (Type I/glial-like cells, Type II/receptor cells, or Type III/presynaptic cells) undergo taste-evoked changes of cAMP and what the functional consequences of such changes are remain unknown. Using Fura-2 imaging of isolated mouse vallate taste cells, we explored how elevating cAMP alters Ca(2+) levels in identified taste cells. Stimulating taste buds with forskolin (Fsk; 1 microm) + isobutylmethylxanthine (IBMX; 100 microm), which elevates cellular cAMP, triggered Ca(2+) transients in 38% of presynaptic cells (n = 128). We used transgenic GAD-GFP mice to show that cAMP-triggered Ca(2+) responses occur only in the subset of presynaptic cells that lack glutamic acid decarboxylase 67 (GAD). We never observed cAMP-stimulated responses in receptor cells, glial-like cells or GAD-expressing presynaptic cells. The response to cAMP was blocked by the protein kinase A inhibitor H89 and by removing extracellular Ca(2+). Thus, the response to elevated cAMP is a PKA-dependent influx of Ca(2+). This Ca(2+) influx was blocked by nifedipine (an inhibitor of L-type voltage-gated Ca(2+) channels) but was unperturbed by omega-agatoxin IVA and omega-conotoxin GVIA (P/Q-type and N-type channel inhibitors, respectively). Single-cell RT-PCR on functionally identified presynaptic cells from GAD-GFP mice confirmed the pharmacological analyses: Ca(v)1.2 (an L-type subunit) is expressed in cells that display cAMP-triggered Ca(2+) influx, while Ca(v)2.1 (a P/Q subunit) is expressed in all presynaptic cells, and underlies depolarization-triggered Ca(2+) influx. Collectively, these data demonstrate cross-talk between cAMP and Ca(2+) signalling in a subclass of taste cells that form synapses with gustatory fibres and may integrate tastant-evoked signals.
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Affiliation(s)
- Craig D Roberts
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL 33136, USA
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29
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Ishimaru Y. Molecular mechanisms of taste transduction in vertebrates. Odontology 2009; 97:1-7. [DOI: 10.1007/s10266-008-0095-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Accepted: 11/07/2008] [Indexed: 12/18/2022]
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Abstract
In the soft palate, tongue, pharynx and larynx surrounding the oral region, taste buds are present, allowing the sensation of taste. On the tongue surface, 3 kinds of papillae are present: fungiform, foliate, and circumvallate. Approximately 5,000 taste buds cover the surface of the human tongue, with about 30% fungiform, 30% foliate and 40% circumvallate papillae. Each taste bud comprises 4 kinds of cells, namely high dark (type I), low light (type II), and intermediate (type III) cells in electron density and Merkel-like taste basal cells (type IV) located at a distance from taste pores. Type II cells sense taste stimuli and type III cells transmit taste signals to sensory afferent nerve fibers. However, type I and type IV cells are not considered to possess obvious taste functions. Synaptic interactions that mediate communication in taste cells provide signal outputs to primary afferent fibers. In the study of taste bud cells, molecular functional techniques using single cells have recently been applied. Serotonin (5-HT) plays a role in cell-to-cell transmission of taste signals. ATP fills the criterion of a neurotransmitter that activates receptors of taste nerve fibers. Findings on 5-HT and ATP suggest that various different transmitters and receptors are present in taste buds. However, no firm evidence for taste-evoked release from type III cells has been identified, except for 5-HT and ATP. These results suggest that different transmitters and receptors may not be present in taste buds. Accordingly, an understanding of how transmitters might function remains elusive.
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Affiliation(s)
- Takashi Suzuki
- Department of Physiology, Tokyo Dental College, Chiba, Japan.
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31
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A study of the science of taste: On the origins and influence of the core ideas. Behav Brain Sci 2008; 31:59-75; discussion 75-105. [DOI: 10.1017/s0140525x08003348] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
AbstractOur understanding of the sense of taste is largely based on research designed and interpreted in terms of the traditional four “basic” tastes: sweet, sour, salty, and bitter, and now a few more. This concept of basic tastes has no rational definition to test, and thus it has not been tested. As a demonstration, a preliminary attempt to test one common but arbitrary psychophysical definition of basic tastes is included in this article; that the basic tastes are unique in being able to account for other tastes. This definition was falsified in that other stimuli do about as well as the basic words and stimuli. To the extent that this finding might show analogies with other studies of receptor, neural, and psychophysical phenomena, the validity of the century-long literature of the science of taste based on a few “basics” is called into question. The possible origins, meaning, and influence of this concept are discussed. Tests of the model with control studies are suggested in all areas of taste related to basic tastes. As a stronger alternative to the basic tradition, the advantages of the across-fiber pattern model are discussed; it is based on a rational data-based hypothesis, and has survived attempts at falsification. Such “population coding” has found broad acceptance in many neural systems.
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Abstract
AbstractWhy has the labeled line versus across-fiber pattern debate of taste coding not been resolved? Erickson suggests that the basic tastes concept has no rational definition to test. Similarly, however, taste neuron types, which are fundamental to the across-fiber pattern concept, have not been formally defined, leaving this concept with no rational definition to test. Consequently, the two concepts are largely indistinguishable.
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Basic tastes as cognitive concepts and taste coding as more than spatial. Behav Brain Sci 2008. [DOI: 10.1017/s0140525x08003385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AbstractErickson's treatise intertwines and confuses two major, but separable, issues: whether there are basic tastes and how taste stimuli are encoded. The idea of basic tastes may reflect a natural process of concept formation. By only discussing two spatial coding schemes for taste, Erickson ignores the temporal dimension of taste responses and the contribution of neuronal cooperativity.
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Glendinning JI. How do predators cope with chemically defended foods? THE BIOLOGICAL BULLETIN 2007; 213:252-266. [PMID: 18083965 DOI: 10.2307/25066643] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Many prey species (including plants) deter predators with defensive chemicals. These defensive chemicals act by rendering the prey's tissues noxious, toxic, or both. Here, I explore how predators cope with the presence of these chemicals in their diet. First, I describe the chemosensory mechanisms by which predators (including herbivores) detect defensive chemicals. Second, I review the mechanisms by which predators either avoid or tolerate defensive chemicals in prey. Third, I examine how effectively free-ranging predators can overcome the chemical defenses of prey. The available evidence indicates that predators have mixed success overcoming these defenses. This conclusion is based on reports of free-ranging predators rejecting unpalatable but harmless prey, or voluntarily ingesting toxic prey.
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Affiliation(s)
- John I Glendinning
- Department of Biological Sciences, Barnard College, Columbia University, 3009 Broadway, New York, New York 10027, USA.
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Abstract
Although there have been many recent advances in the field of gustatory neurobiology, our knowledge of how the nervous system is organized to process information about taste is still far from complete. Many studies on this topic have focused on understanding how gustatory neural circuits are spatially organized to represent information about taste quality (e.g., "sweet", "salty", "bitter", etc.). Arguments pertaining to this issue have largely centered on whether taste is carried by dedicated neural channels or a pattern of activity across a neural population. But there is now mounting evidence that the timing of neural events may also importantly contribute to the representation of taste. In this review, we attempt to summarize recent findings in the field that pertain to these issues. Both space and time are variables likely related to the mechanism of the gustatory neural code: information about taste appears to reside in spatial and temporal patterns of activation in gustatory neurons. What is more, the organization of the taste network in the brain would suggest that the parameters of space and time extend to the neural processing of gustatory information on a much grander scale.
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Affiliation(s)
- Christian H Lemon
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, 855 Monroe Ave., Suite 515, Memphis, TN 38163, USA
| | - Donald B Katz
- Department of Psychology and Volen National Center for Complex Systems, Brandeis University, Volen 208/MS 013, 415 South St., Waltham, MA 02454, USA
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Bigiani A, Cuoghi V. Localization of amiloride-sensitive sodium current and voltage-gated calcium currents in rat fungiform taste cells. J Neurophysiol 2007; 98:2483-7. [PMID: 17686911 DOI: 10.1152/jn.00716.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recent studies have shown that taste cells transducing bitter, sweet, and umami stimuli do not possess high-threshold voltage-gated calcium channels required for synaptic transmission at conventional synapses, suggesting some sort of signal processing inside taste buds prior to the activation of nerve endings. To evaluate whether this is a general paradigm for the physiology of taste reception, we studied the transduction pathway underlying the detection of sodium ions (salty stimulus). In laboratory rodents, Na(+) is thought to be transduced, at least in part, through amiloride-sensitive sodium channels (ASSCs). Therefore we used the patch-clamp techniques to analyze the occurrence pattern of amiloride-sensitive sodium currents and voltage-gated calcium currents (both low-voltage-activated T-type current and high-voltage-activated L-type current) among taste cells in rat fungiform papillae. Because taste cells turnover, we focused our attention on cells possessing large voltage-gated sodium currents, a sign of "mature" cells. We found that cells expressing functional ASSCs either did not possess any calcium currents or exhibited only T-type calcium currents, which is believed to play a role in repetitive firing. On the contrary, cells lacking functional ASSCs were endowed with L-type calcium currents, which are thought to mediate calcium influx required for neurotransmitter exocytosis. Therefore our data suggest that sodium-detecting cells are unlikely to use conventional synaptic communication to transfer taste information to nerve endings. Our findings on sodium taste detection support the recent model of taste transduction, involving separate groups of taste cells: chemosensitive cells and cells forming conventional synapses.
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Affiliation(s)
- Albertino Bigiani
- Dipartimento di Scienze Biomediche, Università di Modena e Reggio Emilia, Modena, Italy.
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37
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Roper SD. Signal transduction and information processing in mammalian taste buds. Pflugers Arch 2007; 454:759-76. [PMID: 17468883 PMCID: PMC3723147 DOI: 10.1007/s00424-007-0247-x] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2006] [Accepted: 01/04/2007] [Indexed: 10/23/2022]
Abstract
The molecular machinery for chemosensory transduction in taste buds has received considerable attention within the last decade. Consequently, we now know a great deal about sweet, bitter, and umami taste mechanisms and are gaining ground rapidly on salty and sour transduction. Sweet, bitter, and umami tastes are transduced by G-protein-coupled receptors. Salty taste may be transduced by epithelial Na channels similar to those found in renal tissues. Sour transduction appears to be initiated by intracellular acidification acting on acid-sensitive membrane proteins. Once a taste signal is generated in a taste cell, the subsequent steps involve secretion of neurotransmitters, including ATP and serotonin. It is now recognized that the cells responding to sweet, bitter, and umami taste stimuli do not possess synapses and instead secrete the neurotransmitter ATP via a novel mechanism not involving conventional vesicular exocytosis. ATP is believed to excite primary sensory afferent fibers that convey gustatory signals to the brain. In contrast, taste cells that do have synapses release serotonin in response to gustatory stimulation. The postsynaptic targets of serotonin have not yet been identified. Finally, ATP secreted from receptor cells also acts on neighboring taste cells to stimulate their release of serotonin. This suggests that there is important information processing and signal coding taking place in the mammalian taste bud after gustatory stimulation.
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Affiliation(s)
- Stephen D Roper
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA.
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38
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Yoshida R, Yasumatsu K, Shigemura N, Ninomiya Y. Coding channels for taste perception: information transmission from taste cells to gustatory nerve fibers. ACTA ACUST UNITED AC 2007; 69:233-42. [PMID: 17287578 DOI: 10.1679/aohc.69.233] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Taste signals are first detected by the taste receptor cells, which are located in taste buds existing in the tongue, soft palate, larynx and epiglottis. Taste receptor cells contact with the chemical compounds in oral cavity through the apical processes which protrude into the taste pore. Interaction between chemical compounds and the taste receptor produces activation of taste receptor cells directly or indirectly. Then the signals are transmitted to gustatory nerve fibers and higher order neurons. A recent study demonstrated many similarities between response properties of taste receptor cells with action potentials and those of the gustatory nerve fibers innervating them, suggesting information derived from receptor cells generating action potentials may form a major component of taste information that is transmitted to gustatory nerve fibers. These findings may also indicate that there is no major modification of taste information sampled by taste receptor cells in synaptic transmission from taste cells to nerve fibers although there is indirect evidence. In the peripheral taste system, gustatory nerve fibers may selectively contact with taste receptor cells that have similar response properties and convey constant taste information to the higher order neurons.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Japan
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Watson KJ, Kim I, Baquero AF, Burks CA, Liu L, Gilbertson TA. Expression of aquaporin water channels in rat taste buds. Chem Senses 2007; 32:411-21. [PMID: 17339611 DOI: 10.1093/chemse/bjm006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In order to gain insight into the molecular mechanisms that allow taste cells to respond to changes in their osmotic environment, we have used primarily immunocytochemical and molecular approaches to look for evidence of the presence of aquaporin-like water channels in taste cells. Labeling of isolated taste buds from the fungiform, foliate, and vallate papillae in rat tongue with antibodies against several of the aquaporins (AQPs) revealed the presence of AQP1, AQP2, and AQP5 in taste cells from these areas. AQP3 antibodies failed to label isolated taste buds from any of the papillae. There was an apparent difference in the regional localization of AQP labeling within the taste bud. Antibodies against AQP1 and AQP2 labeled predominantly the basolateral membrane, whereas the AQP5 label was clearly evident on both the apical and basolateral membranes of cells within the taste bud. Double labeling revealed that AQP1 and AQP2 labeled many, but not all, of the same taste cells. Similar double-labeling experiments with anti-AQP2 and anti-AQP5 clearly showed that AQP5 was expressed on or near the apical membranes whereas AQP2 was absent from this area. The presence of these 3 types of AQPs in taste buds but not in non-taste bud-containing epithelia was confirmed using reverse transcription-polymerase chain reaction. Experiments using patch clamp recording showed that the AQP inhibitor, tetraethylammonium, significantly reduced hypoosmotic-induced currents in rat taste cells. We hypothesize that the AQPs may play roles both in the water movement underlying compensatory mechanisms for changes in extracellular osmolarity and, in the case of AQP5 in particular, in the gustatory response to water.
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Affiliation(s)
- Kristina J Watson
- Department of Biology and The Center for Advanced Nutrition, Utah State University, Logan, UT 84322-5305, USA.
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Simon SA, de Araujo IE, Gutierrez R, Nicolelis MAL. The neural mechanisms of gustation: a distributed processing code. Nat Rev Neurosci 2007; 7:890-901. [PMID: 17053812 DOI: 10.1038/nrn2006] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Whenever food is placed in the mouth, taste receptors are stimulated. Simultaneously, different types of sensory fibre that monitor several food attributes such as texture, temperature and odour are activated. Here, we evaluate taste and oral somatosensory peripheral transduction mechanisms as well as the multi-sensory integrative functions of the central pathways that support the complex sensations that we usually associate with gustation. On the basis of recent experimental data, we argue that these brain circuits make use of distributed ensemble codes that represent the sensory and post-ingestive properties of tastants.
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Affiliation(s)
- Sidney A Simon
- Department of Neurobiology, Duke University, Durham, North Carolina 27710, USA.
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Abstract
The emerging picture of taste coding at the periphery is one of elegant simplicity. Contrary to what was generally believed, it is now clear that distinct cell types expressing unique receptors are tuned to detect each of the five basic tastes: sweet, sour, bitter, salty and umami. Importantly, receptor cells for each taste quality function as dedicated sensors wired to elicit stereotypic responses.
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Affiliation(s)
- Jayaram Chandrashekar
- Howard Hughes Medical Institute and Departments of Neurobiology and Neurosciences, University of California at San Diego, La Jolla, California 92093-0649, USA
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Yoshida R, Shigemura N, Sanematsu K, Yasumatsu K, Ishizuka S, Ninomiya Y. Taste Responsiveness of Fungiform Taste Cells With Action Potentials. J Neurophysiol 2006; 96:3088-95. [PMID: 16971686 DOI: 10.1152/jn.00409.2006] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It is known that a subset of taste cells generate action potentials in response to taste stimuli. However, responsiveness of these cells to particular tastants remains unknown. In the present study, by using a newly developed extracellular recording technique, we recorded action potentials from the basolateral membrane of single receptor cells in response to taste stimuli applied apically to taste buds isolated from mouse fungiform papillae. By this method, we examined taste-cell responses to stimuli representing the four basic taste qualities (NaCl, Na saccharin, HCl, and quinine-HCl). Of 72 cells responding to taste stimuli, 48 (67%) responded to one, 22 (30%) to two, and 2 (3%) to three of four taste stimuli. The entropy value presenting the breadth of responsiveness was 0.158 ± 0.234 (mean ± SD), which was close to that for the nerve fibers (0.183 ± 0.262). In addition, the proportion of taste cells predominantly sensitive to each of the four taste stimuli, and the grouping of taste cells based on hierarchical cluster analysis, were comparable with those of chorda tympani (CT) fibers. The occurrence of each class of taste cells with different taste responsiveness to the four taste stimuli was not significantly different from that of CT fibers except for classes with broad taste responsiveness. These results suggest that information derived from taste cells generating action potentials may provide the major component of taste information that is transmitted to gustatory nerve fibers.
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Affiliation(s)
- Ryusuke Yoshida
- Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Spector AC, Travers SP. The representation of taste quality in the mammalian nervous system. ACTA ACUST UNITED AC 2006; 4:143-91. [PMID: 16510892 DOI: 10.1177/1534582305280031] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The process by which the mammalian nervous system represents the features of a sapid stimulus that lead to a perception of taste quality has long been controversial. The labeled-line (sparse coding) view differs from the across-neuron pattern (ensemble) counterpoint in proposing that activity in a given class of neurons is necessary and sufficient to generate a specific taste perception. This article critically reviews molecular, electro-physiological, and behavioral findings that bear on the issue. In the peripheral gustatory system, the authors conclude that most qualities appear to be signaled by labeled lines; however, elements of both types of coding characterize signaling of sodium salts. Given the heterogeneity of neuronal tuning functions in the brain, the central coding mechanism is less clear. Both sparse coding and neuronal ensemble models remain viable possibilities. Furthermore, temporal patterns of discharge could contribute additional information. Ultimately, until specific classes of neurons can be selectively manipulated and perceptual consequences assessed, it will be difficult to go beyond mere correlation and conclusively discern the validity of these coding models.
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Affiliation(s)
- Alan C Spector
- Department of Psychology and Center for Smell and Taste, University of Florida
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Mal RK, Birchall MA. Dysgeusia related to urinary obstruction from benign prostatic disease: a case control and qualitative study. Eur Arch Otorhinolaryngol 2005; 263:176-9. [PMID: 16133464 DOI: 10.1007/s00405-005-0973-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Anecdotal reports suggest that dysgeusia may be related to a variety of systemic factors, including bladder outflow obstruction. This is a hospital-based case-controlled study involving 111 patients who were admitted to urological wards for transurethral resection of the prostate for benign prostatic disease with age- and sex-matched control of 137 subjects. We used a semi-structured questionnaire by a trained interviewer at admission (preoperative), at the postoperative period and at follow-up between 4-6 months (median 5 months). Analysis used unpaired t-test and chi(2) test. The incidence of dysgeusia was 22% in the study group and 13% in the control group (P=N.S.). However, strikingly, the dysgeusia in the study group was relieved promptly by relief of urinary obstruction in 100% of cases and did not return within the follow-up period. The mechanism of the dysgeusia associated with dysuria in benign prostatic disease is unknown, but we suggest that the dysgeusia could be from the stress of dysuria or due to a release of an unknown chemical from the urinary tract or an overflow of neural impulse from pontine/cortical micturition centres to the taste centres. An association between dysgeusia and dysuria has not been described before.
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Affiliation(s)
- R K Mal
- Department of Otolaryngology, University of Bristol, Southmead Hospital, Bristol, BS10 5ND, UK.
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Lemon CH, Smith DV. Neural representation of bitter taste in the nucleus of the solitary tract. J Neurophysiol 2005; 94:3719-29. [PMID: 16107527 DOI: 10.1152/jn.00700.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Based on the molecular findings that many bitter taste receptors (T2Rs) are expressed within the same receptor cells, it has been proposed that bitter taste is encoded by the activation of discrete neural elements. Here we examined how a variety of bitter stimuli are represented by neural activity in central gustatory neurons. Taste responses (spikes/s) evoked by bathing the tongue and palate with intensity-matched concentrations (in M) of 2 sugars (0.32 sucrose and 0.5 D-fructose), ethanol (40%), 4 salts (0.01 NaCl, 0.008 NaNO(3), 0.01 MgCl(2), and 0.05 KCl), 2 acids (0.003 HCl and 0.005 citric acid), and 10 bitter ligands (0.007 quinine-HCl, 0.015 denatonium benzoate, 0.003 l-cysteine, 0.001 nicotine, 0.005 strychnine-HCl, 0.04 tetraethylammonium chloride, 0.03 atropine-SO(4), 0.005 brucine-SO(4), 0.03 papaverine-HCl, and 0.009 sparteine) were recorded from 51 neurons in the nucleus of the solitary tract of anesthetized rats. Cluster analysis was used to categorize neurons into types based on responses to sucrose, NaCl, HCl, and quinine-HCl. Three groupings emerged: type S (responded optimally to sweets), type N (sodium-optimal), and type H/Q (responded robustly to bitters, acids, and salts). Multivariate analyses revealed that across-neuron patterns of response among bitter stimuli were strongly correlated. However, neural type H/Q, which was most responsive to bitter tastants, was not differentially sensitive to bitter stimuli and Na(+) salts, which rats perceive as distinct. Thus central neurons most responsive to bitter substances receive significant input from receptors that mediate other tastes, indicating that bitter stimuli are not represented by activity in specifically tuned neurons.
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Affiliation(s)
- Christian H Lemon
- Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, Memphis, 38163, USA
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Frank ME, Formaker BK, Hettinger TP. Peripheral gustatory processing of sweet stimuli by golden hamsters. Brain Res Bull 2005; 66:70-84. [PMID: 15925146 DOI: 10.1016/j.brainresbull.2005.04.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 04/01/2005] [Accepted: 04/04/2005] [Indexed: 11/27/2022]
Abstract
Behaviors and taste-nerve responses to bitter stimuli are linked to compounds that bind T2 receptors expressed in one subset of taste-bud receptor cells (TRCs); and behavioral and neural responses to sweet stimuli are linked to chemical compounds that bind a T1 receptor expressed in a different TRC subset. Neural and behavioral responses to bitter-sweet mixtures, however, complicate the ostensible bitter and sweet labeled lines. In the golden hamster, Mesocricetus auratus, quinine hydrochloride, the bitter prototype, suppresses chorda tympani (CT) nerve responses to the sweet prototype: sucrose. This bitter-sweet inhibition was tested with concentration series of sucrose and dulcin, a hydrophobic synthetic sweetener that hamsters behaviorally cross-generalize with sucrose. Dulcin, sucrose and other sweeteners activate one subset of CT fibers: S neurons; whereas, quinine activates a separate subset of CT fibers: E neurons. Whole-nerve and S-neuron CT responses to a sweetener concentration series, mixed with 0, 1, 3 and 10 mM quinine, were measured for 0-2.5 s transient and/or 2.6-10 s steady-state response periods. Ten-sec total single-fiber records, aligned at response onset, were averaged for 100 ms bins to identify response oscillations. Quinine inhibition of dulcin and sucrose responses was identical. Each log molar increment in quinine resulted in equivalent declines in response to either sweetener. Furthermore, sucrose response decrements paralleled response increments in quinine-sensitive CT neurons to the same quinine increases. A 1.43 Hz bursting rhythm to the sweeteners was unchanged by quinine inhibition or decreases in sweetener concentration. Taste-bud processing, possibly between-cell inhibition and within-cell negative feedback, must modify signals initiated by T1 receptors before they are transmitted to the brain.
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Affiliation(s)
- Marion E Frank
- Neurosciences, Department of Oral Health and Diagnostic Sciences, School of Dental Medicine, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-1605, USA.
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Spector AC. The functional organization of the peripheral gustatory system: Lessons from behavior. PROGRESS IN PSYCHOBIOLOGY AND PHYSIOLOGICAL PSYCHOLOGY 2005. [DOI: 10.1016/s0363-0951(03)80008-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
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Sollars SI, Hill DL. In vivo recordings from rat geniculate ganglia: taste response properties of individual greater superficial petrosal and chorda tympani neurones. J Physiol 2005; 564:877-93. [PMID: 15746166 PMCID: PMC1464453 DOI: 10.1113/jphysiol.2005.083741] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Coding of gustatory information is complex and unique among sensory systems; information is received by multiple receptor populations located throughout the oral cavity and carried to a single central relay by four separate nerves. The geniculate ganglion is the location of the somata of two of these nerves, the greater superficial petrosal (GSP) and the chorda tympani (CT). The GSP innervates taste buds on the palate and the CT innervates taste buds on the anterior tongue. To obtain requisite taste response profiles of GSP neurones, we recorded neurophysiological responses to taste stimuli of individual geniculate ganglion neurones in vivo in the rat and compared them to those from the CT. GSP neurones had a distinct pattern of responding compared to CT neurones. For example, a small subset of GSP neurones had high response frequencies to sucrose stimulation, whereas no CT neurones had high response frequencies to sucrose. In contrast, NaCl elicited high response frequencies in a small subset of CT neurones and elicited moderate response frequencies in a relatively large proportion of GSP neurones. The robust whole-nerve response to sucrose in the GSP may be attributable to relatively few, narrowly tuned neurones, whereas the response to NaCl in the GSP may relate to proportionately more, widely tuned neurones. These results demonstrate the diversity in the initial stages of sensory coding for two separate gustatory nerves involved in the ingestion or rejection of taste solutions, and may have implications for central coding of gustatory quality and concentration as well as coding of information used in controlling energy, fluid and electrolyte homeostasis.
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Affiliation(s)
- Suzanne I Sollars
- Department of Psychology, University of Nebraska Omaha, Omaha, NE 68182, USA.
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Duda T, Sharma RK. S100B-modulated Ca2+-dependent ROS-GC1 transduction machinery in the gustatory epithelium: a new mechanism in gustatory transduction. FEBS Lett 2005; 577:393-8. [PMID: 15556616 DOI: 10.1016/j.febslet.2004.09.089] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 09/07/2004] [Accepted: 09/09/2004] [Indexed: 10/26/2022]
Abstract
Gustatory transduction is a biochemical process by which the gustatory signal generates the electric signal. The microvilli of the taste cells in the gustatory epithelium are the sites of gustatory transduction. This study documents the biochemical, molecular, and functional identity of the Ca2+-modulated membrane guanylate cyclase transduction machinery in the bovine gustatory epithelium. The machinery is a two-component system: the Ca2+-sensor protein, S100B; and the transducer, ROS-GC1. S100B senses increments in free Ca2+, undergoes conformational change, binds to the domain amino acids (aa) Gly962-Asn981 and via the transduction domain aa Ile1030-Gln1041 activates ROS-GC1, generating the second messenger, cyclic GMP. In a recent study, operational presence of this machinery has been demonstrated in the photoreceptor bipolar synapse [Duda et al., EMBO J. 21 (2002) 2547]. Thus, the machinery has a broader role in sensory perceptions, vision in the retinal neurons and gustation in the tongue. The entry of the ROS-GC transduction machinery defines the beginning of a new paradigm of Ca2+ signaling in the tongue.
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Affiliation(s)
- Teresa Duda
- The Unit of Regulatory and Molecular Biology, Department of Cell Biology, SOM & NJMS, University of Medicine and Dentistry of New Jersey, Stratford, NJ 08084, USA.
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