1985 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Maturation &Reinnervation of Submandibular Ganglia @ University of Colorado Denver
neural plasticity; neural transmission; autonomic ganglion; synapses; vagotomy; denervation; axon; heart rate; innervation; parasympathetic nervous system; nervous system regeneration; fresh water environment; electron microscopy; electrophysiology; online computer;
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0.943 |
1985 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Maturation and Reinnervation of Rat Submandibular Gangli @ Colorado State University-Fort Collins |
0.928 |
1985 — 1991 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neural Influence On Aging of Receptor Cells @ Colorado State University-Fort Collins
The vertebrate taste bud is a good model for studying cellular aging in the nervous system. Taste cells possess many characteristics shared by neurons, such as excitability, chemosensitivity, and synapses (Roper, 1983a; Kinnamon, Taylor, Delay and Roper, 1985; Kinnamon and Roper, 1986). Taste cells have the added advantage that their lifespan is short (only a few days) compared to neurons, and thus age-related changes can be measured with reliability and confidence: complicating factors such as metabolic or hormonal differences between young and old animals are avoided. Furthermore, detailed analyses of age- related changes in the biophysical properties of taste cells and in their membrane chemosensitivity can be conducted on taste cells. Taste cells from the mudpuppy (Necturus maculosus) will be impaled with microelectrodes in situ, using a new isolated preparation developed in this laboratory (Roper, 1983). In depth analyses of the membrane conductances, particularly potassium conductance, will shed light on how ionic channels change over the lifespan of an excitable cell. Chemical stimuli will be applied focally onto the apical surface of taste cells to sutdy what age- related changes in chemosensitivity occur. Cells will be impaled with dye-filled micropipettes to identify the cells in subsequent light and electron micrographs in order to correlate the functional properites of the cell with its age: recent observations have indicated that taste cell aging can be determined by ultrastructural features (Kinnamon, et al. 1985; Delay, Kinnamon and Roper, 1986). These findings will provide information on cellular aging in excitable tissues and will also lead to a better understanding of taste transduction mechanisms.
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0.943 |
1986 — 2012 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Chemosensory Transduction in Taste Cells @ Colorado State University-Fort Collins
The long term objective of this project is two-fold. First, our aim is to study cell-to-cell communication in the taste bud. One of our Specific Aims is to investigate which neurotransmitters are involved at synapses in taste organs. We plan to use a battery of neurochemical and molecular biological techniques, including immunocytochemistry, quantitative autoradiography, high pressure liquid chromatography with electrochemical detection, and polymerase chain reactions to investigate transmitters. We will determine which transmitters are present in taste buds; which ones are taken up by taste cells and released by calcium-dependent mechanisms when the cells are stimulated; where the transmitters are localized; which transmitter receptors are expressed in taste cells; and where these postsynaptic receptors are expressed. A major focus of the studies will be on the possible neurotransmitter role of biogenic amines and on amino acid transmitters, particularly gamma aminobutyric acid (GABA) and glutamate. Other transmitter and neuromodulator candidates, especially neuropeptides, will also be investigated. We will also apply patch clamp recording techniques in a new preparation, the lingual slice, to study electrical synapses between taste cells. We will use a novel method for monitoring electrical connections in the living isolated taste bud and test whether taste stimulation (e.g. acids) change the properties of the electrical connections. We will also test whether neuromodulators such as serotonin affect electrical coupling between taste cells. Second, we will use the new lingual slice preparation to study how chemical stimuli affect the apical, chemosensory surface of taste receptor cells. Our Specific Aim here is to determine whether taste cells are "tuned" to one or only a few chemical stimuli or whether taste cells respond broadly to a number of different, unrelated chemical stimuli. We will use patch recording techniques to record receptor current evoked by focal application of chemical stimuli onto the apical pore of taste buds isolated in the lingual slice preparation. The project will focus on how two specific classes of chemical stimuli, acids and calcium salts, affect taste receptor cells. These are both important taste stimuli in man and animals. Acids generally taste sour and calcium salts often are bitter. We will test several hypotheses that have been put forth to explain transduction of these chemicals, such as decreases in apical potassium conductance, influx of protons, involvement of ion transporters. We will patch clamp taste receptor cells and analyze membrane conductance changes, if any, elicited by these chemical stimuli. In the broad view, our experiments may lead to the rational design of pharmaceutical agents that can suppress, enhance or modify taste since we will determine what neurotransmitters are acting in the taste organs and since our data will lead to an understanding of how chemicals act on the apical, chemosensory membrane of taste cells. Our study will also bear on all chemosensitive cells, generally, such as pH receptors, wherever they occur in the central and peripheral nervous system.
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1 |
1986 |
Roper, Stephen D. |
R13Activity Code Description: To support recipient sponsored and directed international, national or regional meetings, conferences and workshops. |
From Reception to Perceptor--International Symposium @ University of Colorado Denver
This application requests support for a program consisting of symposia, conferences, and workshops which will be held in conjunction with the 9th triennial meeting of the International Symposium on Olfaction and Taste (ISOT) and the 8th annual meeting of the Association for Chemoreception Sciences (AChemS). The aims of these symposia, conferences, and workshops are to identify new, promising directions and areas of research; to discuss controversial issues of research not usually covered by more traditional chemosensory meetings; to encourage interdisciplinary collaboration among investigators in order to stimualte unique research directions; to educate young investigators; to provide the opportunity for new, promising investigators to present their findings; to encourage participation of international scientists; to attract physicians and clinical investigators; to propose approaches to solving current problems in the chemical senses, including chemosensory disorders and associated disease states in the mission of the NINCDS; and to publish the proceedings of the meeting in a widely-read journal. Timely topics for the meeting have been chosen by the ISOT Organizing Committee from the suggestions of members of AChemS, the European Chemoreception Research Organization (ECRO), the Japanese Association for the Study of Taste and Smell (JASTS), and with the advice of the International Commission on Olfaction and Taste (ICOT). The programs have been reviewed by the ISOT Organizing Committee to ensure their quality and significance to chemosensory research and to disorders and the mission of the NINCDS. The topics and the faculty of the program are described. Described also is a new format for ISOT and a novel way of programming the meeting. To arrive at new approaches for studying the chemical senses, leading experts in fields related to taste and olfaction, namely chemical reception in ciliated protozoa and bacteria, and even sensory processing in audition, will play important roles. The conference has been approved for substantial credits for Continuing Medical Education to attract physicians and clinical workers. To encourage international participation, the proposed meeting will be a satellite of the 1986 International Union of Physiological Sciences (IUPS) conference held in Vancouver, British Columbia.
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0.943 |
1991 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neurotransmission in the Taste Bud @ Colorado State University-Fort Collins
Chemosensory mechanisms in the vertebrate taste bud have eluded detailed analyses until recently, mainly due to the relative inaccessibility of the taste cells. A particularly important question is how signals are processed in the peripheral taste organs. Ultrastructural studies have shown that there are synapses between taste cells and gustatory axons as well as between taste cells, themselves, raising the possibility that there is synaptic processing in the taste bud. We have recently employed a new approach that will allow us to examine the microphysiology of taste cells in a relatively intact, but exposed preparation and to begin to answer these questions. This preparation consists of a thin slice of lingual epithelium, mounted in a shallow. transparent chamber in such a way that entire taste buds and their cells can be visualized in the living isolated tissue. The objective of the following proposal is to test the hypothesis that there are synaptic connections among cells in the taste bud and that the final output, activity in gustatory sensory axons, represents a complex integration of signals from several different cells within the taste bud. Thus, we propose the following specific aims for the project: 1) We propose to confirm and extend our preliminary findings suggesting that there are synaptic connections between receptor and basal cells: 2) We will examine the properties of these synaptic connections, namely their Ca-dependence, neurotransmitter type, ionic mechanisms and response to repetitive and/or prolonged activation: 3) We will determine whether synaptic connections between receptor cells and basal cells are bidirectional and/or reciprocal, as their morphology suggests. The results of these studies will provide information relevant to signal processing in chemosensory receptor organs in general, such as carotid body responses. Furthermore, the data may provide a baseline for studying the question of how taste stimuli are coded in the vertebrate taste bud.
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0.928 |
1992 — 1993 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Neurotransmission in the Vertebrate Taste Bud @ Colorado State University-Fort Collins
Chemosensory mechanisms in the vertebrate taste bud have eluded detailed analyses until recently, mainly due to the relative inaccessibility of the taste cells. A particularly important question is how signals are processed in the peripheral taste organs. Ultrastructural studies have shown that there are synapses between taste cells and gustatory axons as well as between taste cells, themselves, raising the possibility that there is synaptic processing in the taste bud. We have recently employed a new approach that will allow us to examine the microphysiology of taste cells in a relatively intact, but exposed preparation and to begin to answer these questions. This preparation consists of a thin slice of lingual epithelium, mounted in a shallow. transparent chamber in such a way that entire taste buds and their cells can be visualized in the living isolated tissue. The objective of the following proposal is to test the hypothesis that there are synaptic connections among cells in the taste bud and that the final output, activity in gustatory sensory axons, represents a complex integration of signals from several different cells within the taste bud. Thus, we propose the following specific aims for the project: 1) We propose to confirm and extend our preliminary findings suggesting that there are synaptic connections between receptor and basal cells: 2) We will examine the properties of these synaptic connections, namely their Ca-dependence, neurotransmitter type, ionic mechanisms and response to repetitive and/or prolonged activation: 3) We will determine whether synaptic connections between receptor cells and basal cells are bidirectional and/or reciprocal, as their morphology suggests. The results of these studies will provide information relevant to signal processing in chemosensory receptor organs in general, such as carotid body responses. Furthermore, the data may provide a baseline for studying the question of how taste stimuli are coded in the vertebrate taste bud.
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0.928 |
1993 — 1997 |
Roper, Stephen D |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Neurotransmission and Neuromodulation in Peripheral Taste Organs @ University of Colorado Denver
The long-term objective of this project is twofold. First, our aim is to study cell-to-cell communication in the vertebrate taste buds. We will investigate taste buds in amphibia (Necturus maculosus) and in mammals (hamsters, rabbits, mice). One of our Specific Aims is to investigate which neurotransmitters are involved at synapses in taste organs. We plan to use a battery of neurochemical and molecular biological techniques, including immunocytochemistry, quantitative autoradiography, and high pressure liquid chromatography with electrochemical detection. We will determine which transmitters are present in taste buds; which ones are taken up by taste cells and released by calcium-dependent mechanisms when the cells are stimulated; and where the transmitters are localized. We will also study electrical synapses between taste cells and the localization of gap junction proteins. Second, we will study the function of Merkel-like basal cells and their putative role in neuromodulation of taste bud function. Merkel-like basal cells contain high concentrations of serotonin, among other substances and release the monoamine when they are depolarized. We will investigate whether serotonin is a neuromodulator of taste bud function in amphibia and in mammals. In the broad view, our experiments may lead to the rational design of pharmaceutical agents that can suppress, enhance or modify taste since we will determine what neurotransmitters are acting in the taste organs and since our data will lead to an understanding of how chemicals act on the apical, chemosensory membrane of taste cells.
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0.943 |
1996 — 2002 |
Roper, Stephen D. |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Localization of Glutamate Receptors in Taste Buds @ University of Miami School of Medicine
L-Glutamate (as in monosodium glutamate, MSG) is an important free amino acid constituent of many foodstuffs. Many researchers believe the taste of MSG differs fundamentally from sweet, sour, salty, and bitter MSG elicits a complex taste that has been umami. MSG stimulates food intake in humans and animals alike. In taste buds, transduction for MSG appears to be distinct from other taste qualities. As described in the Overview, we hypothesize that taste bud cells transduce this amino acid via apical receptors similar to glutamate receptors found in the brain. More specifically, we postulate that a metabotropic glutamate receptor similar to mGluR4 a G protein-coupled receptor found at synapses in the brain is central in MS taste transduction. During the current funding period, we discovered that rat taste bud cells express a unique variant of mGluR4 and that stimulation of this novel receptor appears to mimic aspects of glutamate taste. In addition, however, other glutamate receptors may be present in taste bud cells and participate in glutamate taste transduction. Conceivably, glutamate activates multiple receptor mechanisms in taste bud cells. Thus, a complete explanation of MSG taste transduction may involve more than one receptor mechanism. Indeed, this notion forms the working hypothesis for our study. The intent of the studies proposed in Project #2 is twofold. First, the experiments will provide morphological correlates for the molecular and functional studies described in Projects 1 and 3. That is, we will use in situ hybridization and immunocytochemistry to visualize glutamate receptors in taste buds. Second, the experiments will extend the analyses being conducted at the molecular and membrane levels to the level of sensory afferent fibers and ultimately animal behavioral responses. We will collaborate with two leading laboratories in the fields of chemical senses and animal behavior to record responses from single gustatory afferent fibers and to conduct detailed taste synergy and taste discrimination studies. By combining a multi-disciplinary approach at several levels of analysis, we hope to contribute significantly to an understanding of how taste bud cells transduce MSG taste.
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1 |
1998 — 2002 |
Roper, Stephen D. |
P01Activity Code Description: For the support of a broadly based, multidisciplinary, often long-term research program which has a specific major objective or a basic theme. A program project generally involves the organized efforts of relatively large groups, members of which are conducting research projects designed to elucidate the various aspects or components of this objective. Each research project is usually under the leadership of an established investigator. The grant can provide support for certain basic resources used by these groups in the program, including clinical components, the sharing of which facilitates the total research effort. A program project is directed toward a range of problems having a central research focus, in contrast to the usually narrower thrust of the traditional research project. Each project supported through this mechanism should contribute or be directly related to the common theme of the total research effort. These scientifically meritorious projects should demonstrate an essential element of unity and interdependence, i.e., a system of research activities and projects directed toward a well-defined research program goal. |
Identifying Neurotransmitters Released From Taste Cells @ University of Colorado Denver
The long term objective of this project is to identify the transmitter or transmitters at synapses in mammalian taste buds. Taste receptor cells make synaptic connections with afferent terminals from sensory ganglion cells. Taste receptor cells also are believed to form lateral synaptic connections with other taste bud cells in the peripheral organs of taste, i.e., intrinsic or intragemmal synaptic interactions. Additionally, efferent axons may synapse with taste bud cells. By analogy with other sensory organs, one might speculate that glutamate (glu), acetylcholine (Ach), serotonin (5HT) and norepinephrine (NE) are released at these synaptic sites. However, the identity of neurotransmitters in taste buds is not yet known. This lack of information has greatly slowed an analysis of peripheral taste mechanisms in health and disease. We propose 3 Specific Aim to fill this gap in information about taste bud synapses. Fist, we will use quantitative autoradiography and immunocytochemistry to study the uptake of 5HT, NE and glu in mouse taste buds. We will test if there are specific re-uptake mechanisms in taste cells for these transmitter candidates. In collaboration with J. Kinnamon (Project #3), we will determine the ultrastructure of the taste cells that accumulate these transmitters and correlate transmitter identification with synaptic markers. Second, we will use the same techniques along with new biosensor methodologies and carbon fiber electrode voltammetry, to test whether 5HT, NE, glu and ACh are released by synapses in mouse taste buds. We will determine whether the release is Ca-dependent, and whether stimulating taste buds with taste stimuli (sweet, bitter, salty, etc.) releases different transmitters. One series in these experiments will be conducted in the laboratory of S. Kinnamon (Project #5). Third, we will employ immunocytochemistry and in situ hybridization to examine the expression of transmitter receptors in taste buds and their innervating sensory neurons. Although the focus of our Specific Aims is on glu, ACh, 5HT and NE, we will keep an open mind and explore the possibility that transmitters other than these may be released. At the end of the project, we will have identified one or more of the key neurotransmitters released at synaptic sites in mammalian taste buds.
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0.943 |
2003 — 2016 |
Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) R55Activity Code Description: Undocumented code - click on the grant title for more information. |
A New Method to Measure Taste Bud Function @ University of Miami School of Medicine
DESCRIPTION (provided by applicant): This proposal investigates synaptic transmitters in mammalian taste buds. My Specific Aims include identifying the principal transmitters released by mouse taste cells during gustatory stimulation and determining where these transmitters act. Transmitters that have been identified to date and shown to be released by taste cells include serotonin, ATP, and norepinephrine. However, there is strong evidence that there are others, including glutamate, acetylcholine, and certain peptides. To complete the Aims, we will use a biosensor technique we developed and optimized in the previous funding period. Our biosensors consist of genetically-engineered CHO cells that are very sensitive to specific transmitters. We will use functional Ca2+ imaging to measure taste-evoked activity in taste cells and biosensors. We will correlate our findings with immunostaining for the receptors, transporters, and biosynthetic enzymes of candidate transmitters to confirm their presence and action in taste buds. This approach will allow us to answer such questions as: what are the transmitters in taste buds? Are there different transmitters for different tastes? How do taste cells interact via these transmitters? The long-term goal of this project is to construct a diagram of synaptic interactions that take place in the taste bud during taste stimulation. Understanding these interactions may help explain how different tastes (sweet, sour, salty, bitter, umami) are discriminated.
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1 |
2012 — 2013 |
Chaudhari, Nirupa (co-PI) [⬀] Roper, Stephen D. |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Imaging Taste in Ensembles of Afferent Neurons @ University of Miami School of Medicine
DESCRIPTION (provided by applicant): This multi-PI R21 proposal describes a high-risk, high-impact project that introduces a novel method for recording taste-evoked activity in gustatory afferent neurons. The work represents a major new direction for the PIs as well as for the chemical senses community, and thus is ideally suited for the R21 mechanism. The project will introduce a novel recording technique to produce new data on the taste sensitivities and transmitter systems of large ensembles of geniculate ganglion neurons. We will employ a new strain of genetically-engineered mice that express a fluorescent functional reporter, GCaMP3, selectively in sensory (including gustatory) ganglion neurons. We propose to develop a new recording technique to image taste-evoked activity in fluorescent geniculate ganglion neurons in anesthetized mice. Geniculate neurons will be imaged with scanning laser confocal microscopy and changes in fluorescence quantified to simultaneously measure activity in large ensembles of neurons with single cell resolution. Ganglion cells will be excited by prototypic sweet, bitter salty, sour, umami and fat taste stimuli, delivered in the oral cavity. We will measure the breadth of tuning, concentration-response relations and entropy for gustatory geniculate ganglion cells (Aim 1). Functionally characterized neurons will be isolated and single cell RT-PCR will be carried out to examine the neurotransmitter systems employed by functionally distinct taste neurons (Aim2). Successful completion of the two aims will have 4 outcomes: first, we will have developed a completely new method for recording afferent sensory activity in large numbers of gustatory neurons~ second, we will accumulate a large database of response profiles for gustatory afferent axons, providing a comprehensive catalog of their breadth of tuning and entropies~ third, we will determine whether different classes of sensory neurons (generalists~ specialists~ sweet-, sour-sensing, etc.) have different molecular expression profiles, such as distinctive transmitter systems, transcription factors, and so forth~ and finally, whether there i a unique class of fat-sensing geniculate ganglion neurons. The data will have implications for how taste is coded by sensory afferents (e.g., labeled line vs, combinatorial coding) and will tremendously increase our understanding about how sensory neurons process gustatory signals.
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1 |
2015 — 2019 |
Chaudhari, Nirupa (co-PI) [⬀] Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Imaging Molecules and Circuits in Peripheral Taste Pathways @ University of Miami School of Medicine
DESCRIPTION (provided by applicant): We have developed an innovative method to record taste-evoked activity in gustatory afferent neurons with good cellular and temporal resolution. The method uses confocal functional calcium imaging and transgenic mice that express GCaMP3 in sensory neurons. By carefully exposing geniculate ganglia in living, anesthetized GCaMP3-mice and applying taste stimuli to the oral cavity, we can now record robust and reliable responses to discern the principles behind the transmission of gustatory evoked signals from taste buds to the hindbrain. These data will considerably extend single unit electrical recordings from the chorda tympani and greater superficial petrosal nerves or from geniculate ganglion cells. We are able to recording simultaneously from large ensembles of neurons. We have also designed a powerful strategy to relate the functional response profiles of individual geniculate ganglion neurons to their patterns of gene expression and establish robust molecular markers for separate functional classes of neurons. In a concerted effort from two well-established laboratories, we now propose a multi-PI project to exploit this novel preparation and to answer key questions regarding taste. Our new approach will tremendously expand our knowledge of peripheral sensory processing in taste. Our preliminary data demonstrate the feasibility of all 4 tightly-focused Specific Aims: Aim 1: How do gustatory sensory afferent cells respond to sweet, salty, bitter, sour, umami tastes and fats? Aim 2: Do mixtures of taste stimuli enhance responses from gustatory sensory afferent neurons? Aim 3: Do ganglion neurons that express certain transmitter receptors innervate specific taste cells? Aim 4: Are there dedicated neurons that detect each taste stimulus, and if so, can specific molecular markers be identified that associate with gustatory afferent neuron responses for each taste quality?
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1 |
2017 — 2018 |
Roper, Stephen D. |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Orosensory Pain Following Oxaliplatin Chemotherapy @ University of Miami School of Medicine
Project Summary Orofacial pain is excruciating. Indeed, trigeminal neuralgia, a severe form of orofacial pain, has been termed ?suicide disease? for reasons that need no explanation. The important platinum-based chemotherapeutic, oxaliplatin (Eloxatin®), commonly prescribed for colorectal cancer, produces serious off-target sensory neuropathies that include orofacial pain, cold allodynia, and abnormal oral sensations. These side effects can make it difficult for a cancer patient to consume food and beverages and can lead to drug intolerance and non- compliance. Not only is the patient her/himself deeply affected and depressed by these side-effects, but equally important, care-givers become entangled with special meal-preparations, food requirements, and general oversight. In short, chemotherapy-induced orofacial pain and oral sensory disturbances are serious problems. Finding remedies for these sensory neuropathies is paramount. Hyperalgesia and allodynia, including chemotherapy-induced neurotoxicity, have long been attributed to heightened sensitivity of sensory afferent fibers and/or sensitization of dorsal horn neurons. However, an innovative explanation has recently been postulated: allodynia and hyperalgesia are caused by abnormal coupling between sensory ganglion cells, mediated by reactive satellite glial cells. Specifically, the anti-cancer drug oxaliplatin is hypothesized to increase gap junction communication among satellite glia and generate pathological neuron-to-glia-to-neuron interactions, i.e. neural coupling within sensory ganglia. This groundbreaking hypothesis is founded mainly on compelling data from in vitro studies. If validated in vivo, this new understanding of neuropathic pain is particularly exciting because sensory ganglia lie outside the blood brain barrier. They are readily accessible to i.v. administration of therapeutic drugs. The present proposal outlines key in vivo tests of the above hypothesis regarding abnormal neuronal coupling in the trigeminal ganglion due to off-target side effects of cancer chemotherapy, particularly oxaliplatin-induced cold allodynia. We will use a recently-developed mouse model of oxaliplatin therapy combined with a new method for imaging sensory ganglion cell activity in living mice. We propose to record responses of trigeminal ganglion sensory neurons that innervate the oral cavity before and after oxaliplatin treatments that mimic chemotherapy in humans. We will use scanning laser confocal Ca2+ imaging in genetically-engineered mice in which sensory neurons express the Ca2+-sensitive reporter GCaMP. We will test for orosensory hyperalgesia such as cold allodynia after oxaliplatin treatment and for the development of neuronal crosstalk within the trigeminal ganglion that might underlie such hypersensitivity. Importantly, findings from this study may have general implications for understanding allodynia and hypersensitivity beyond orofacial pain.
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1 |
2020 |
Chaudhari, Nirupa (co-PI) [⬀] Roper, Stephen D. |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Functions of Gustatory Afferent Neuron Types. @ University of Miami School of Medicine
Project Summary Single-cell RNA sequencing (scRNAseq) has made unprecedented strides in discovering previously unrecognized diversity of neuronal cell types and their functions. Using scRNAseq, we showed that the mouse geniculate ganglion contains 3 molecularly distinct types of gustatory neurons that innervate taste buds, T1, T2, and T3, each with unique patterns of gene expression. In a concerted effort from two well-established laboratories, we now propose a multi-PI project to test hypotheses regarding distinct functions for each of the major types of neurons and their subtypes. Our ultimate goal is to produce an integrated molecular and functional categorization of gustatory neurons similar to what has been so powerfully effective in the auditory, visual, and somatosensory systems. We propose using a newly-optimized method for in vivo confocal Ca2+ imaging, neuron-selective fluorescent markers, and chemogenetic silencing to reveal the functions of T1 and T3 geniculate ganglion neurons. Specifically, using GCaMP-based Ca2+ imaging, we will test the hypothesis that within the cluster of T1 neurons there are subclasses that respond to distinct taste qualities whereas neurons within the T3 cluster respond to multiple, convergent tastes. We will further test the hypothesis that T1 and T3 neuronal subtypes contribute to separate central pathways serving a number of taste-dependent functions downstream of initial detection in the taste periphery. Completing the above aims will move the field of taste into a new era of molecular-functional integration. Our findings will assist electrophysiology and circuit tracing studies in taste, will shed light on the controversy over labeled lines versus combinatorial taste coding, and will bring new information on gustatory neural pathways that are so important to nutrition and ingestive behavior.
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