1
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Kawai F. Somatic ion channels and action potentials in olfactory receptor cells and vomeronasal receptor cells. J Neurophysiol 2024; 131:455-471. [PMID: 38264787 DOI: 10.1152/jn.00137.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 01/10/2024] [Accepted: 01/17/2024] [Indexed: 01/25/2024] Open
Abstract
Olfactory receptor cells are primary sensory neurons that catch odor molecules in the olfactory system, and vomeronasal receptor cells catch pheromones in the vomeronasal system. When odor or pheromone molecules bind to receptor proteins expressed on the membrane of the olfactory cilia or vomeronasal microvilli, receptor potentials are generated in their receptor cells. This initial excitation is transmitted to the soma via dendrites, and action potentials are generated in the soma and/or axon and transmitted to the central nervous system. Thus, olfactory and vomeronasal receptor cells play an important role in converting chemical signals into electrical signals. In this review, the electrophysiological characteristics of ion channels in the somatic membrane of olfactory receptor cells and vomeronasal receptor cells in various species are described and the differences between the action potential dynamics of olfactory receptor cells and vomeronasal receptor cells are compared.
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Affiliation(s)
- Fusao Kawai
- Department of Physiology, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan
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2
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Fukutani Y, Abe M, Saito H, Eguchi R, Tazawa T, de March CA, Yohda M, Matsunami H. Antagonistic interactions between odorants alter human odor perception. Curr Biol 2023; 33:2235-2245.e4. [PMID: 37220745 PMCID: PMC10394640 DOI: 10.1016/j.cub.2023.04.072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Revised: 03/19/2023] [Accepted: 04/27/2023] [Indexed: 05/25/2023]
Abstract
The olfactory system uses hundreds of odorant receptors (ORs), the largest group of the G-protein-coupled receptor (GPCR) superfamily, to detect a vast array of odorants. Each OR is activated by specific odorous ligands, and like other GPCRs, antagonism can block activation of ORs. Recent studies suggest that odorant antagonisms in mixtures influence olfactory neuron activities, but it is unclear how this affects perception of odor mixtures. In this study, we identified a set of human ORs activated by methanethiol and hydrogen sulfide, two potent volatile sulfur malodors, through large-scale heterologous expression. Screening odorants that block OR activation in heterologous cells identified a set of antagonists, including β-ionone. Sensory evaluation in humans revealed that β-ionone reduced the odor intensity and unpleasantness of methanethiol. Additionally, suppression was not observed when methanethiol and β-ionone were introduced simultaneously to different nostrils. Our study supports the hypothesis that odor sensation is altered through antagonistic interactions at the OR level.
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Affiliation(s)
- Yosuke Fukutani
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
| | - Masashi Abe
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Haruka Saito
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan
| | - Ryo Eguchi
- Research Section, R & D Division, S.T. Corporation, Shinjuku, Tokyo 161-0033, Japan
| | - Toshiaki Tazawa
- Research Section, R & D Division, S.T. Corporation, Shinjuku, Tokyo 161-0033, Japan
| | - Claire A de March
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Institute of Chemistry of the Natural Substances, Université Paris Saclay, CNRS UPR2301, Gif-sur-Yvette 91190, France
| | - Masafumi Yohda
- Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan; Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan.
| | - Hiroaki Matsunami
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan; Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Neurobiology, Duke Institute for Brain Sciences, Duke University Medical Center, Durham, NC 27705, USA.
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3
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Berners-Lee A, Shtrahman E, Grimaud J, Murthy VN. Experience-dependent evolution of odor mixture representations in piriform cortex. PLoS Biol 2023; 21:e3002086. [PMID: 37098044 PMCID: PMC10129003 DOI: 10.1371/journal.pbio.3002086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 03/17/2023] [Indexed: 04/26/2023] Open
Abstract
Rodents can learn from exposure to rewarding odors to make better and quicker decisions. The piriform cortex is thought to be important for learning complex odor associations; however, it is not understood exactly how it learns to remember discriminations between many, sometimes overlapping, odor mixtures. We investigated how odor mixtures are represented in the posterior piriform cortex (pPC) of mice while they learn to discriminate a unique target odor mixture against hundreds of nontarget mixtures. We find that a significant proportion of pPC neurons discriminate between the target and all other nontarget odor mixtures. Neurons that prefer the target odor mixture tend to respond with brief increases in firing rate at odor onset compared to other neurons, which exhibit sustained and/or decreased firing. We allowed mice to continue training after they had reached high levels of performance and find that pPC neurons become more selective for target odor mixtures as well as for randomly chosen repeated nontarget odor mixtures that mice did not have to discriminate from other nontargets. These single unit changes during overtraining are accompanied by better categorization decoding at the population level, even though behavioral metrics of mice such as reward rate and latency to respond do not change. However, when difficult ambiguous trial types are introduced, the robustness of the target selectivity is correlated with better performance on the difficult trials. Taken together, these data reveal pPC as a dynamic and robust system that can optimize for both current and possible future task demands at once.
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Affiliation(s)
- Alice Berners-Lee
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
| | - Elizabeth Shtrahman
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
| | - Julien Grimaud
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
- Cell Engineering Laboratory (CellTechs), Sup'Biotech, Villejuif, France
| | - Venkatesh N Murthy
- Department of Molecular and Cellular Biology and Center for Brain Science, Harvard University, Cambridge, Massachusetts, United States of America
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4
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Scarano F, Deivarajan Suresh M, Tiraboschi E, Cabirol A, Nouvian M, Nowotny T, Haase A. Geosmin suppresses defensive behaviour and elicits unusual neural responses in honey bees. Sci Rep 2023; 13:3851. [PMID: 36890201 PMCID: PMC9995521 DOI: 10.1038/s41598-023-30796-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 03/01/2023] [Indexed: 03/10/2023] Open
Abstract
Geosmin is an odorant produced by bacteria in moist soil. It has been found to be extraordinarily relevant to some insects, but the reasons for this are not yet fully understood. Here we report the first tests of the effect of geosmin on honey bees. A stinging assay showed that the defensive behaviour elicited by the bee's alarm pheromone component isoamyl acetate (IAA) is strongly suppressed by geosmin. Surprisingly, the suppression is, however, only present at very low geosmin concentrations, and disappears at higher concentrations. We investigated the underlying mechanisms at the level of the olfactory receptor neurons by means of electroantennography, finding the responses to mixtures of geosmin and IAA to be lower than to pure IAA, suggesting an interaction of both compounds at the olfactory receptor level. Calcium imaging of the antennal lobe (AL) revealed that neuronal responses to geosmin decreased with increasing concentration, correlating well with the observed behaviour. Computational modelling of odour transduction and coding in the AL suggests that a broader activation of olfactory receptor types by geosmin in combination with lateral inhibition could lead to the observed non-monotonic increasing-decreasing responses to geosmin and thus underlie the specificity of the behavioural response to low geosmin concentrations.
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Affiliation(s)
- Florencia Scarano
- Department of Physics, University of Trento, 38120, Trento, Italy.,Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068, Rovereto, Italy
| | | | - Ettore Tiraboschi
- Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068, Rovereto, Italy
| | - Amélie Cabirol
- Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068, Rovereto, Italy.,Department of Fundamental Microbiology, University of Lausanne, CH-1015, Lausanne, Switzerland
| | - Morgane Nouvian
- Department of Biology, University of Konstanz, 78457, Konstanz, Germany.,Zukunftskolleg, University of Konstanz, 78464, Konstanz, Germany
| | - Thomas Nowotny
- School of Engineering and Informatics, University of Sussex, Brighton, BN1 9QJ, UK.
| | - Albrecht Haase
- Department of Physics, University of Trento, 38120, Trento, Italy. .,Center for Mind/Brain Sciences (CIMeC), University of Trento, 38068, Rovereto, Italy.
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5
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Adefuin AM, Lindeman S, Reinert JK, Fukunaga I. State-dependent representations of mixtures by the olfactory bulb. eLife 2022; 11:76882. [PMID: 35254262 PMCID: PMC8937304 DOI: 10.7554/elife.76882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 03/05/2022] [Indexed: 12/02/2022] Open
Abstract
Sensory systems are often tasked to analyse complex signals from the environment, separating relevant from irrelevant parts. This process of decomposing signals is challenging when a mixture of signals does not equal the sum of its parts, leading to an unpredictable corruption of signal patterns. In olfaction, nonlinear summation is prevalent at various stages of sensory processing. Here, we investigate how the olfactory system deals with binary mixtures of odours under different brain states by two-photon imaging of olfactory bulb (OB) output neurons. Unlike previous studies using anaesthetised animals, we found that mixture summation is more linear in the early phase of evoked responses in awake, head-fixed mice performing an odour detection task, due to dampened responses. Despite smaller and more variable responses, decoding analyses indicated that the data from behaving mice was well discriminable. Curiously, the time course of decoding accuracy did not correlate strictly with the linearity of summation. Further, a comparison with naïve mice indicated that learning to accurately perform the mixture detection task is not accompanied by more linear mixture summation. Finally, using a simulation, we demonstrate that, while saturating sublinearity tends to degrade the discriminability, the extent of the impairment may depend on other factors, including pattern decorrelation. Altogether, our results demonstrate that the mixture representation in the primary olfactory area is state-dependent, but the analytical perception may not strictly correlate with linearity in summation.
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Affiliation(s)
- Aliya Mari Adefuin
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Sander Lindeman
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Janine K Reinert
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
| | - Izumi Fukunaga
- Sensory and Behavioural Neuroscience Unit, Okinawa Institute of Science and Technology Graduate University, Okinawa, Japan
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6
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Yuan Q, Qin C, Duan Y, Jiang N, Liu M, Wan H, Zhuang L, Wang P. An in vivo bioelectronic nose for possible quantitative evaluation of odor masking using M/T cell spatial response patterns. Analyst 2021; 147:178-186. [PMID: 34870643 DOI: 10.1039/d1an01569a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Odor masking is a prominent phenomenon in the biological olfactory perception system. It has been applied in industry and daily life to develop masking agents to reduce or even eliminate the adverse effects of unpleasant odors. However, it is challenging to assess the odor masking efficiency with traditional gas sensors. Here, we took advantage of the olfactory perception system of an animal to develop a system for the evaluation and quantification of odor masking based on an in vivo bioelectronic nose. The linear decomposition method was used to extract the features of the spatial response pattern of the mitral/tufted (M/T) cell population of the olfactory bulb of a rat to monomolecular odorants and their binary mixtures. Finally, the masking intensity was calculated to quantitatively measure the degree of interference of one odor to another in the biological olfactory system. Compared with the human sensory evaluation reported in a previous study, the trend of masking intensity obtained with this system positively correlated with the human olfactory system. The system could quantitatively analyze the masking efficiency of masking agents, as well as assist in the development of new masking agents or flavored food in odor or food companies.
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Affiliation(s)
- Qunchen Yuan
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China. .,The MOE Frontier Science Center for Brain Science & Brain-machine Integration, Zhejiang University, Hangzhou 310027, China.
| | - Chunlian Qin
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Yan Duan
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Nan Jiang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Mengxue Liu
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Hao Wan
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China. .,State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China.,Binjiang Institute of Zhejiang University, Hangzhou, 310053, China
| | - Liujing Zhuang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China. .,The MOE Frontier Science Center for Brain Science & Brain-machine Integration, Zhejiang University, Hangzhou 310027, China. .,State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China
| | - Ping Wang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China. .,The MOE Frontier Science Center for Brain Science & Brain-machine Integration, Zhejiang University, Hangzhou 310027, China. .,State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China.,Binjiang Institute of Zhejiang University, Hangzhou, 310053, China
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7
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Lebovich L, Yunerman M, Scaiewicz V, Loewenstein Y, Rokni D. Paradoxical relationship between speed and accuracy in olfactory figure-background segregation. PLoS Comput Biol 2021; 17:e1009674. [PMID: 34871306 PMCID: PMC8675919 DOI: 10.1371/journal.pcbi.1009674] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 12/16/2021] [Accepted: 11/20/2021] [Indexed: 11/19/2022] Open
Abstract
In natural settings, many stimuli impinge on our sensory organs simultaneously. Parsing these sensory stimuli into perceptual objects is a fundamental task faced by all sensory systems. Similar to other sensory modalities, increased odor backgrounds decrease the detectability of target odors by the olfactory system. The mechanisms by which background odors interfere with the detection and identification of target odors are unknown. Here we utilized the framework of the Drift Diffusion Model (DDM) to consider possible interference mechanisms in an odor detection task. We first considered pure effects of background odors on either signal or noise in the decision-making dynamics and showed that these produce different predictions about decision accuracy and speed. To test these predictions, we trained mice to detect target odors that are embedded in random background mixtures in a two-alternative choice task. In this task, the inter-trial interval was independent of behavioral reaction times to avoid motivating rapid responses. We found that increased backgrounds reduce mouse performance but paradoxically also decrease reaction times, suggesting that noise in the decision making process is increased by backgrounds. We further assessed the contributions of background effects on both noise and signal by fitting the DDM to the behavioral data. The models showed that background odors affect both the signal and the noise, but that the paradoxical relationship between trial difficulty and reaction time is caused by the added noise. Sensory systems are constantly stimulated by signals from many objects in the environment. Segmentation of important signals from the cluttered background is therefore a task that is faced by all sensory systems. For many mammalians, the sense of smell is the primary sense that guides many daily behaviors. As such, the olfactory system must be able to detect and identify odors of interest against varying and dynamic backgrounds. Here we studied how background odors interfere with the detection of target odors. We trained mice on a task in which they are presented with odor mixtures and are required to report whether they include either of two target odors. We analyze the behavioral data using a common model of sensory-guided decision-making—the drift-diffusion-model. In this model, decisions are influenced by two elements: a drift which is the signal produced by the stimulus, and noise. We show that the addition of background odors has a dual effect—a reduction in the drift, as well as an increase in the noise. The increased noise also causes more rapid decisions, thereby producing a paradoxical relationship between trial difficulty and decision speed; mice make faster decisions on more difficult trials.
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Affiliation(s)
- Lior Lebovich
- The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel
| | - Michael Yunerman
- Department of Medical Neurobiology, School of Medicine and IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Viviana Scaiewicz
- Department of Medical Neurobiology, School of Medicine and IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Yonatan Loewenstein
- The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel
- The Alexander Silberman Institute of Life Sciences, The Hebrew University, Jerusalem, Israel
- Department of Cognitive Sciences and The Federmann Center for the Study of Rationality, The Hebrew University, Jerusalem, Israel
| | - Dan Rokni
- Department of Medical Neurobiology, School of Medicine and IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
- * E-mail:
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8
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Gronowitz ME, Liu A, Qiu Q, Yu CR, Cleland TA. A physicochemical model of odor sampling. PLoS Comput Biol 2021; 17:e1009054. [PMID: 34115747 PMCID: PMC8221795 DOI: 10.1371/journal.pcbi.1009054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 06/23/2021] [Accepted: 05/09/2021] [Indexed: 11/19/2022] Open
Abstract
We present a general physicochemical sampling model for olfaction, based on established pharmacological laws, in which arbitrary combinations of odorant ligands and receptors can be generated and their individual and collective effects on odor representations and olfactory performance measured. Individual odor ligands exhibit receptor-specific affinities and efficacies; that is, they may bind strongly or weakly to a given receptor, and can act as strong agonists, weak agonists, partial agonists, or antagonists. Ligands interacting with common receptors compete with one another for dwell time; these competitive interactions appropriately simulate the degeneracy that fundamentally defines the capacities and limitations of odorant sampling. The outcome of these competing ligand-receptor interactions yields a pattern of receptor activation levels, thereafter mapped to glomerular presynaptic activation levels based on the convergence of sensory neuron axons. The metric of greatest interest is the mean discrimination sensitivity, a measure of how effectively the olfactory system at this level is able to recognize a small change in the physicochemical quality of a stimulus. This model presents several significant outcomes, both expected and surprising. First, adding additional receptors reliably improves the system’s discrimination sensitivity. Second, in contrast, adding additional ligands to an odorscene initially can improve discrimination sensitivity, but eventually will reduce it as the number of ligands increases. Third, the presence of antagonistic ligand-receptor interactions produced clear benefits for sensory system performance, generating higher absolute discrimination sensitivities and increasing the numbers of competing ligands that could be present before discrimination sensitivity began to be impaired. Finally, the model correctly reflects and explains the modest reduction in odor discrimination sensitivity exhibited by transgenic mice in which the specificity of glomerular targeting by primary olfactory neurons is partially disrupted. We understand most sensory systems by comparing the responses of the system against objective external physical measurements. For example, we know that our ability to distinguish small changes in color is greater for some colors than for others, and that we can distinguish sounds more acutely when they are within the range of pitches used for speech. Similar principles presumably apply to the sense of smell, but odorous chemicals are harder to physically quantify than light or sound because they cannot be organized in terms of a straightforward physical variable like wavelength or frequency. That said, the physical properties of interactions between chemicals and cellular receptors (such as those in the olfactory system) are well understood. What we lack is a systematic framework within which these pharmacological principles can be organized to study odor sampling in the way that we have long studied visual and auditory sampling. We here propose and describe such a framework for odor sampling, and show that it successfully replicates some established but unexplained experimental results.
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Affiliation(s)
- Mitchell E. Gronowitz
- Department of Psychology, Cornell University, Ithaca, New York, United States of America
| | - Adam Liu
- Department of Psychology, Cornell University, Ithaca, New York, United States of America
| | - Qiang Qiu
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
| | - C. Ron Yu
- Stowers Institute for Medical Research, Kansas City, Missouri, United States of America
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas, United States of America
| | - Thomas A. Cleland
- Department of Psychology, Cornell University, Ithaca, New York, United States of America
- * E-mail:
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9
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Abstract
There is increasing appreciation that G-protein-coupled receptors (GPCRs) can initiate diverse cellular responses by activating multiple G proteins, arrestins, and other biochemical effectors. Structurally different ligands targeting the same receptor are thought to stabilize the receptor in multiple distinct active conformations such that specific subsets of signaling effectors are engaged at the exclusion of others, creating a bias toward a particular outcome, which has been referred to as ligand-induced selective signaling, biased agonism, ligand-directed signaling, and functional selectivity, among others. The potential involvement of functional selectivity in mammalian olfactory signal transduction has received little attention, notwithstanding the fact that mammalian olfactory receptors comprise the largest family of mammalian GPCRs. This position review considers the possibility that, although such complexity in G-protein function may have been lost in the specialization of olfactory receptors to serve as sensory receptors, the ability of olfactory receptor neurons (ORNs) to function as signal integrators and growing appreciation that this functionality is widespread in the receptor population suggest otherwise. We pose that functional selectivity driving 2 opponent inputs have the potential to generate an output that reflects the balance of ligand-dependent signaling, the direction of which could be either suppressive or synergistic and, as such, needs to be considered as a mechanistic basis for signal integration in mammalian ORNs.
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Affiliation(s)
- Barry W Ache
- Whitney Laboratory, Departments of Biology and Neuroscience, and Center for Smell and Taste, University of Florida, Gainesville, FL, USA
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10
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Corey EA, Ukhanov K, Bobkov YV, McIntyre JC, Martens JR, Ache BW. Inhibitory signaling in mammalian olfactory transduction potentially mediated by Gα o. Mol Cell Neurosci 2020; 110:103585. [PMID: 33358996 DOI: 10.1016/j.mcn.2020.103585] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 11/27/2020] [Accepted: 12/09/2020] [Indexed: 01/12/2023] Open
Abstract
Olfactory GPCRs (ORs) in mammalian olfactory receptor neurons (ORNs) mediate excitation through the Gαs family member Gαolf. Here we tentatively associate a second G protein, Gαo, with inhibitory signaling in mammalian olfactory transduction by first showing that odor evoked phosphoinositide 3-kinase (PI3K)-dependent inhibition of signal transduction is absent in the native ORNs of mice carrying a conditional OMP-Cre based knockout of Gαo. We then identify an OR from native rat ORNs that are activated by octanol through cyclic nucleotide signaling and inhibited by citral in a PI3K-dependent manner. We show that the OR activates cyclic nucleotide signaling and PI3K signaling in a manner that reflects its functionality in native ORNs. Our findings lay the groundwork to explore the interesting possibility that ORs can interact with two different G proteins in a functionally identified, ligand-dependent manner to mediate opponent signaling in mature mammalian ORNs.
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Affiliation(s)
- Elizabeth A Corey
- Whitney Laboratory, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America
| | - Kirill Ukhanov
- Dept. of Pharmacology and Therapeutics, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America
| | - Yuriy V Bobkov
- Whitney Laboratory, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America
| | - Jeremy C McIntyre
- Dept. of Neuroscience, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America
| | - Jeffrey R Martens
- Dept. of Pharmacology and Therapeutics, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America
| | - Barry W Ache
- Whitney Laboratory, Dept. of Biology, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America; Whitney Laboratory, Dept. of Neuroscience, Center for Smell and Taste, University of Florida, Gainesville, FL 32610, United States of America.
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11
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Penker S, Licht T, Hofer KT, Rokni D. Mixture Coding and Segmentation in the Anterior Piriform Cortex. Front Syst Neurosci 2020; 14:604718. [PMID: 33328914 PMCID: PMC7710992 DOI: 10.3389/fnsys.2020.604718] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 11/02/2020] [Indexed: 12/14/2022] Open
Abstract
Coding of odorous stimuli has been mostly studied using single isolated stimuli. However, a single sniff of air in a natural environment is likely to introduce airborne chemicals emitted by multiple objects into the nose. The olfactory system is therefore faced with the task of segmenting odor mixtures to identify objects in the presence of rich and often unpredictable backgrounds. The piriform cortex is thought to be the site of object recognition and scene segmentation, yet the nature of its responses to odorant mixtures is largely unknown. In this study, we asked two related questions. (1) How are mixtures represented in the piriform cortex? And (2) Can the identity of individual mixture components be read out from mixture representations in the piriform cortex? To answer these questions, we recorded single unit activity in the piriform cortex of naïve mice while sequentially presenting single odorants and their mixtures. We find that a normalization model explains mixture responses well, both at the single neuron, and at the population level. Additionally, we show that mixture components can be identified from piriform cortical activity by pooling responses of a small population of neurons-in many cases a single neuron is sufficient. These results indicate that piriform cortical representations are well suited to perform figure-background segmentation without the need for learning.
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Affiliation(s)
| | | | | | - Dan Rokni
- Department of Medical Neurobiology, School of Medicine and IMRIC, The Hebrew University of Jerusalem, Jerusalem, Israel
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12
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Zhuang L, Wei X, Jiang N, Yuan Q, Qin C, Jiang D, Liu M, Zhang Y, Wang P. A biohybrid nose for evaluation of odor masking in the peripheral olfactory system. Biosens Bioelectron 2020; 171:112737. [PMID: 33080464 DOI: 10.1016/j.bios.2020.112737] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/13/2020] [Accepted: 10/15/2020] [Indexed: 11/25/2022]
Abstract
Olfaction is a synthetic sense in which odor mixtures elicit emergent perceptions at the expense of perceiving the individual components. The most common result of mixing two odors is masking one component by another. However, there is lack of analytical techniques for measuring the sense of smell, which is mediated by cross-odorant interactions. Here, we propose a biohybrid nose for objective and quantitative evaluation of malodor masking efficiency of perfumed products. This biohybrid nose is constructed by integrating mammalian olfactory epithelium with microelectrode array chip to read out the olfactory information as electrical signal from multiple tissue sites. The intrinsic odor response of olfactory epithelium is found to be represented by widespread spatiotemporal oscillatory activity. The masking efficiency of fragrance is quantified by calculating the relative difference between the malodor and the binary mixture (malodor + fragrance) response patterns. Results indicate that masking efficiency of fragrance is concentration-dependent, whereas completely masking may occurs when fragrance is employed at a concentration 2-3 orders of magnitude higher than malodor. This study demonstrates for the first time that capitalizing on the biological sense of smell to create biohybrid system provides an effective technique to resolve more complex biosensing-related issues such as odor interactions in mixtures.
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Affiliation(s)
- Liujing Zhuang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China; State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China
| | - Xinwei Wei
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Nan Jiang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Qunchen Yuan
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Chunlian Qin
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Deming Jiang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Mengxue Liu
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Yanning Zhang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Ping Wang
- Biosensor National Special Laboratory, Key Laboratory for Biomedical Engineering of Education Ministry, Department of Biomedical Engineering, Zhejiang University, Hangzhou, 310027, China; State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China.
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13
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Pfister P, Smith BC, Evans BJ, Brann JH, Trimmer C, Sheikh M, Arroyave R, Reddy G, Jeong HY, Raps DA, Peterlin Z, Vergassola M, Rogers ME. Odorant Receptor Inhibition Is Fundamental to Odor Encoding. Curr Biol 2020; 30:2574-2587.e6. [PMID: 32470365 DOI: 10.1016/j.cub.2020.04.086] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 03/31/2020] [Accepted: 04/28/2020] [Indexed: 11/18/2022]
Abstract
Most natural odors are complex mixtures of volatile components, competing to bind odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) of the nose. To date, surprisingly little is known about how OR antagonism shapes neuronal representations in the detection layer of the olfactory system. Here, we investigated its prevalence, the degree to which it disrupts OR ensemble activity, and its conservation across phylogenetically related ORs. Calcium imaging microscopy of dissociated OSNs revealed significant inhibition, often complete attenuation, of responses to indole-a commonly occurring volatile associated with both floral and fecal odors-by a set of 36 tested odorants. To confirm an OR mechanism for the observed inhibition, we performed single-cell transcriptomics on OSNs exhibiting specific response profiles to a diagnostic panel of odorants and identified three paralogous receptors-Olfr740, Olfr741, and Olfr743-which, when tested in vitro, recapitulated OSN responses. We screened ten ORs from the Olfr740 gene family with ∼800 perfumery-related odorants spanning a range of chemical scaffolds and functional groups. Over half of these compounds (430) antagonized at least one of the ten ORs. OR activity fitted a mathematical model of competitive receptor binding and suggests normalization of OSN ensemble responses to odorant mixtures is the rule rather than the exception. In summary, we observed OR antagonism occurred frequently and in a combinatorial manner. Thus, extensive receptor-mediated computation of mixture information appears to occur in the olfactory epithelium prior to transmission of odor information to the olfactory bulb.
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Affiliation(s)
- Patrick Pfister
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Benjamin C Smith
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Barry J Evans
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Jessica H Brann
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Casey Trimmer
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Mushhood Sheikh
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Randy Arroyave
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Gautam Reddy
- Department of Physics, UC San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
| | - Hyo-Young Jeong
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Daniel A Raps
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Zita Peterlin
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA
| | - Massimo Vergassola
- Department of Physics, UC San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA
| | - Matthew E Rogers
- Firmenich Incorporated, 250 Plainsboro Road, Plainsboro, NJ 08536, USA.
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14
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Zak JD, Reddy G, Vergassola M, Murthy VN. Antagonistic odor interactions in olfactory sensory neurons are widespread in freely breathing mice. Nat Commun 2020; 11:3350. [PMID: 32620767 PMCID: PMC7335155 DOI: 10.1038/s41467-020-17124-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 06/10/2020] [Indexed: 12/24/2022] Open
Abstract
Odor landscapes contain complex blends of molecules that each activate unique, overlapping populations of olfactory sensory neurons (OSNs). Despite the presence of hundreds of OSN subtypes in many animals, the overlapping nature of odor inputs may lead to saturation of neural responses at the early stages of stimulus encoding. Information loss due to saturation could be mitigated by normalizing mechanisms such as antagonism at the level of receptor-ligand interactions, whose existence and prevalence remains uncertain. By imaging OSN axon terminals in olfactory bulb glomeruli as well as OSN cell bodies within the olfactory epithelium in freely breathing mice, we find widespread antagonistic interactions in binary odor mixtures. In complex mixtures of up to 12 odorants, antagonistic interactions are stronger and more prevalent with increasing mixture complexity. Therefore, antagonism is a common feature of odor mixture encoding in OSNs and helps in normalizing activity to reduce saturation and increase information transfer.
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Affiliation(s)
- Joseph D Zak
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, 02138, USA.
- Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA.
| | - Gautam Reddy
- NSF-Simons Center for Mathematical & Statistical Analysis of Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Massimo Vergassola
- Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, F-75005, France
| | - Venkatesh N Murthy
- Department of Molecular & Cellular Biology, Harvard University, Cambridge, MA, 02138, USA.
- Center for Brain Science, Harvard University, Cambridge, MA, 02138, USA.
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15
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Xu L, Li W, Voleti V, Zou DJ, Hillman EMC, Firestein S. Widespread receptor-driven modulation in peripheral olfactory coding. Science 2020; 368:368/6487/eaaz5390. [PMID: 32273438 DOI: 10.1126/science.aaz5390] [Citation(s) in RCA: 64] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Accepted: 03/09/2020] [Indexed: 12/24/2022]
Abstract
Olfactory responses to single odors have been well characterized but in reality we are continually presented with complex mixtures of odors. We performed high-throughput analysis of single-cell responses to odor blends using Swept Confocally Aligned Planar Excitation (SCAPE) microscopy of intact mouse olfactory epithelium, imaging ~10,000 olfactory sensory neurons in parallel. In large numbers of responding cells, mixtures of odors did not elicit a simple sum of the responses to individual components of the blend. Instead, many neurons exhibited either antagonism or enhancement of their response in the presence of another odor. All eight odors tested acted as both agonists and antagonists at different receptors. We propose that this peripheral modulation of responses increases the capacity of the olfactory system to distinguish complex odor mixtures.
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Affiliation(s)
- Lu Xu
- Department of Biological Sciences, Columbia University in the City of New York, New York, NY, 10027, USA
| | - Wenze Li
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Sciences, Columbia University in the City of New York, New York, NY, 10027, USA
| | - Venkatakaushik Voleti
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Sciences, Columbia University in the City of New York, New York, NY, 10027, USA
| | - Dong-Jing Zou
- Department of Biological Sciences, Columbia University in the City of New York, New York, NY, 10027, USA
| | - Elizabeth M C Hillman
- Laboratory for Functional Optical Imaging, Departments of Biomedical Engineering and Radiology, Zuckerman Mind Brain Behavior Institute and Kavli Institute for Brain Sciences, Columbia University in the City of New York, New York, NY, 10027, USA.
| | - Stuart Firestein
- Department of Biological Sciences, Columbia University in the City of New York, New York, NY, 10027, USA.
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16
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Abstract
2,4,6-Trichloroanisole (TCA) is a well-known, potent off-flavour compound present in various foods and beverages. TCA has been hypothesised to be a universal cause of flavour loss experienced in daily life. Here, however, we show that titres for the suppression of olfactory transducer channels caused by low-quality bananas are much higher than those for that caused by the TCA itself contained in the banana. We resurveyed other components of low-quality bananas and found that bananas also contain an insecticide (chlorpyrifos), and that it suppresses olfactory transducer channels. Other insecticides also suppressed olfactory transducer channels. Hence, even after passing safety examinations, certain insecticides may decrease the quality of foods and beverages by reducing their intrinsic scents.
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17
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Reddy G, Zak JD, Vergassola M, Murthy VN. Antagonism in olfactory receptor neurons and its implications for the perception of odor mixtures. eLife 2018; 7:34958. [PMID: 29687778 PMCID: PMC5915184 DOI: 10.7554/elife.34958] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 03/30/2018] [Indexed: 11/16/2022] Open
Abstract
Natural environments feature mixtures of odorants of diverse quantities, qualities and complexities. Olfactory receptor neurons (ORNs) are the first layer in the sensory pathway and transmit the olfactory signal to higher regions of the brain. Yet, the response of ORNs to mixtures is strongly non-additive, and exhibits antagonistic interactions among odorants. Here, we model the processing of mixtures by mammalian ORNs, focusing on the role of inhibitory mechanisms. We show how antagonism leads to an effective ‘normalization’ of the ensemble ORN response, that is, the distribution of responses of the ORN population induced by any mixture is largely independent of the number of components in the mixture. This property arises from a novel mechanism involving the distinct statistical properties of receptor binding and activation, without any recurrent neuronal circuitry. Normalization allows our encoding model to outperform non-interacting models in odor discrimination tasks, leads to experimentally testable predictions and explains several psychophysical experiments in humans. When ordering in a coffee shop, you probably recognize and enjoy the aroma of freshly roasted coffee beans. But as well as coffee, you can also smell the croissants behind the counter and maybe even the perfume or cologne of the person next to you. Each of these scents consists of a collection of chemicals, or odorants. To distinguish between the aroma of coffee and that of croissants, your brain must group the odorants appropriately and then keep the groups separate from each other. This is not a trivial task. Odorants bind to proteins called odorant receptors found on the surface of cells in the nose called olfactory receptor neurons. But each odorant does not have its own dedicated receptor. Instead, a single odorant will bind to multiple types of odorant receptors, and thus, each olfactory receptor neuron may respond to multiple odorants. So how does the brain encode mixtures of odorants in a way that allows us to distinguish one aroma from another? Reddy, Zak et al. have developed a computational model to explain how this process works. The model assumes that an odorant triggers a response in an olfactory receptor neuron via two steps. First, the odorant binds to an odorant receptor. Second, the bound odorant activates the receptor. But the odorant that binds most strongly to a receptor will not necessarily be the odorant that is best at activating that receptor. This allows a phenomenon called competitive antagonism to occur. This is when one odorant in a mixture binds more strongly to a receptor than the other odorants, but only weakly activates that receptor. In so doing, the strongly bound odorant prevents the other odorants from binding to and activating the receptor. This helps tame the dominating influence of background odors, which might otherwise saturate the responses of individual olfactory receptor neurons. Reddy, Zak et al. show that processes such as competitive antagonism enable olfactory receptor neurons to encode all of the odors within a mixture. The model can explain various phenomena observed in experiments and it adds to our understanding of how the brain generates our sense of smell. The model may also be relevant to other biological systems that must filter weak signals from a dominant background. These include the immune system, which must distinguish a small set of foreign proteins from the much larger number of proteins that make up our bodies.
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Affiliation(s)
- Gautam Reddy
- Department of Physics, University of California, San Diego, La Jolla, United States
| | - Joseph D Zak
- Department of Molecular Cellular Biology, Harvard University, Cambridge, United States.,Center for Brain Science, Harvard University, Cambridge, United States
| | - Massimo Vergassola
- Department of Physics, University of California, San Diego, La Jolla, United States
| | - Venkatesh N Murthy
- Department of Molecular Cellular Biology, Harvard University, Cambridge, United States.,Center for Brain Science, Harvard University, Cambridge, United States
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18
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Muttray A, Moll B, Faas M, Klimek L, Mann W, Konietzko J. Acute Effects of 1,1,1-Trichloroethane on Human Olfactory Functioning. ACTA ACUST UNITED AC 2018. [DOI: 10.1177/194589240401800208] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background Animal experiments indicate that 1,1,1-trichloroethane can cause degeneration of the olfactory epithelium. The effects of 1,1,1-trichloroethane on human odor perception still have not been investigated. The goal of this study was to learn more about acute effects of 1,1,1-trichloroethane. Methods Twelve healthy, nonsmoking students were exposed to 200 and 20 ppm (control) 1,1,1-trichloroethane in an exposure chamber for 4 hours according to a crossover design. Olfactory functioning was investigated with the Sniffin’ Sticks. The test includes the determination of the detection threshold for n-butanol and an odor identification test. Results After 1 hour of exposure to 200 ppm 1,1,1-trichloroethane, no effects on olfactory functioning were observed. After 4 hours, the olfactory threshold for n-butanol was slightly (p = 0.04) elevated. Conclusion The threshold shift may be caused by different mechanisms, including inflammation of the olfactory mucosa or degeneration of receptor cells.
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Affiliation(s)
- Axel Muttray
- Institute of Occupational, Environmental, and Social Medicine and the University of Mainz, Mainz, Germany
| | - Bertram Moll
- Ear, Nose, and Throat Department, University of Mainz, Mainz, Germany
| | - Michael Faas
- Ear, Nose, and Throat Department, University of Mainz, Mainz, Germany
| | - Ludger Klimek
- Ear, Nose, and Throat Department, University of Mainz, Mainz, Germany
| | - Wolf Mann
- Ear, Nose, and Throat Department, University of Mainz, Mainz, Germany
| | - Johannes Konietzko
- Institute of Occupational, Environmental, and Social Medicine and the University of Mainz, Mainz, Germany
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20
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Odor-evoked inhibition of olfactory sensory neurons drives olfactory perception in Drosophila. Nat Commun 2017; 8:1357. [PMID: 29116083 PMCID: PMC5676773 DOI: 10.1038/s41467-017-01185-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 08/24/2017] [Indexed: 11/28/2022] Open
Abstract
Inhibitory response occurs throughout the nervous system, including the peripheral olfactory system. While odor-evoked excitation in peripheral olfactory cells is known to encode odor information, the molecular mechanism and functional roles of odor-evoked inhibition remain largely unknown. Here, we examined Drosophila olfactory sensory neurons and found that inhibitory odors triggered outward receptor currents by reducing the constitutive activities of odorant receptors, inhibiting the basal spike firing in olfactory sensory neurons. Remarkably, this odor-evoked inhibition of olfactory sensory neurons elicited by itself a full range of olfactory behaviors from attraction to avoidance, as did odor-evoked olfactory sensory neuron excitation. These results indicated that peripheral inhibition is comparable to excitation in encoding sensory signals rather than merely regulating excitation. Furthermore, we demonstrated that a bidirectional code with both odor-evoked inhibition and excitation in single olfactory sensory neurons increases the odor-coding capacity, providing a means of efficient sensory encoding. It is well established that odor-evoked excitation in olfactory sensory neurons (OSNs) encodes odor information. Here the authors report that odor-evoked inhibition in OSNs of Drosophila also encodes odor identity, and can in itself drive both attraction and avoidance behaviors.
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21
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Cyclic-nucleotide-gated cation current and Ca2+-activated Cl current elicited by odorant in vertebrate olfactory receptor neurons. Proc Natl Acad Sci U S A 2016; 113:11078-11087. [PMID: 27647918 DOI: 10.1073/pnas.1613891113] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Olfactory transduction in vertebrate olfactory receptor neurons (ORNs) involves primarily a cAMP-signaling cascade that leads to the opening of cyclic-nucleotide-gated (CNG), nonselective cation channels. The consequent Ca2+ influx triggers adaptation but also signal amplification, the latter by opening a Ca2+-activated Cl channel (ANO2) to elicit, unusually, an inward Cl current. Hence the olfactory response has inward CNG and Cl components that are in rapid succession and not easily separable. We report here success in quantitatively separating these two currents with respect to amplitude and time course over a broad range of odorant strengths. Importantly, we found that the Cl current is the predominant component throughout the olfactory dose-response relation, down to the threshold of signaling to the brain. This observation is very surprising given a recent report by others that the olfactory-signal amplification effected by the Ca2+-activated Cl current does not influence the behavioral olfactory threshold in mice.
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22
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Matsubasa T, Gotow N, Gomi Y, Kobayakawa T. A method for psychophysical screening of odorants for use in city gas based on olfactory adaptation tolerance. CHEMOSENS PERCEPT 2016. [DOI: 10.1007/s12078-016-9213-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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23
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Distinct signaling of Drosophila chemoreceptors in olfactory sensory neurons. Proc Natl Acad Sci U S A 2016; 113:E902-11. [PMID: 26831094 DOI: 10.1073/pnas.1518329113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Drosophila, olfactory sensory neurons (OSNs) rely primarily on two types of chemoreceptors, odorant receptors (Ors) and ionotropic receptors (Irs), to convert odor stimuli into neural activity. The cellular signaling of these receptors in their native OSNs remains unclear because of the difficulty of obtaining intracellular recordings from Drosophila OSNs. Here, we developed an antennal preparation that enabled the first recordings (to our knowledge) from targeted Drosophila OSNs through a patch-clamp technique. We found that brief odor pulses triggered graded inward receptor currents with distinct response kinetics and current-voltage relationships between Or- and Ir-driven responses. When stimulated with long-step odors, the receptor current of Ir-expressing OSNs did not adapt. In contrast, Or-expressing OSNs showed a strong Ca(2+)-dependent adaptation. The adaptation-induced changes in odor sensitivity obeyed the Weber-Fechner relation; however, surprisingly, the incremental sensitivity was reduced at low odor backgrounds but increased at high odor backgrounds. Our model for odor adaptation revealed two opposing effects of adaptation, desensitization and prevention of saturation, in dynamically adjusting odor sensitivity and extending the sensory operating range.
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24
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Valdés J, Olivares J, Ponce D, Schmachtenberg O. Analysis of olfactory sensitivity in rainbow trout (Oncorhynchus mykiss) reveals their ability to detect lactic acid, pyruvic acid and four B vitamins. FISH PHYSIOLOGY AND BIOCHEMISTRY 2015; 41:879-885. [PMID: 25864178 DOI: 10.1007/s10695-015-0054-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 04/07/2015] [Indexed: 06/04/2023]
Abstract
Salmonid fishes like the rainbow trout Oncorhynchus mykiss have a highly developed olfactory sense that allows them to perceive some odorants at very low concentrations, such as certain amino acids and bile salts. Previous behavioral and electrophysiological studies in salmonids have shown strong responses to human skin odor. Because this stimulus represents a complex and heterogeneous mixture of components, we sought to determine which odorants contribute to the sensitive detection of human skin odor by salmonids. In vivo electroolfactogram recordings in O. mykiss revealed lactic acid, pyruvic acid and two B vitamins, thiamine and riboflavin, as novel, potent odorants which triggered responses at nanomolar concentrations. Two more B vitamins, nicotinic and pantothenic acid, were detected at micromolar concentrations. These compounds share important roles in cellular energy metabolism, supporting an original role in food search and feeding behavior of this species and most likely other fishes. The olfactory detection of B vitamins by salmonids represents a new paradigm in chemosensation, warranting further investigation in other teleosts.
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Affiliation(s)
- Joaquín Valdés
- Centro Interdisciplinario de Neurociencia de Valparaíso (CINV), Facultad de Ciencias, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Playa Ancha, 2360102, Valparaíso, Chile
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25
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Yoder WM, Gaynor L, Windham E, Lyman M, Munizza O, Setlow B, Bizon JL, Smith DW. Characterizing olfactory binary mixture interactions in Fischer 344 rats using behavioral reaction times. Chem Senses 2015; 40:325-34. [PMID: 25877697 DOI: 10.1093/chemse/bjv014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Response times provide essential subthreshold perceptual data that extend beyond accuracy alone. Behavioral reaction times (RTs) were used to characterize rats' ability to detect individual odorants in a series of complimentary binary odorant mixture ratios. We employed an automated, liquid-dilution olfactometer to train Fischer 344 rats (N = 8) on an odor identification task using nonreinforced probe trials. Binary mixture ratios composed of aliphatic odorants (citral and octanol) were arranged such that relative contributions of the 2 components varied systematically by a factor of 1% (v/v). Odorant concentrations for the target (S+), control (S-), and mixture (S+:S-) odorants were presented relative to threshold for each rat. Rats were initially trained to respond by licking at a spout to obtain liquid reward for either citral or octanol as the reinforced target (S+) odorant. After achieving 100% accuracy, rats were transferred to variable ratio (VR 2) reinforcement for correct responding. Nonreinforced probe trials (2 per block of 22 trials) were tested for each mixture ratio and recorded as either S+ (rats lick-responded in the presence of the mixture) or S- (rats refrained from licking), thereby indicating detection of the trained, S+ odorant. To determine the perceived salience for each ratio, RTs (latency from odorant onset to lick response) were recorded for each trial. Consistent with previous studies, RTs for both odorants were shortest (~150-200ms) when the probe trials consisted of a single, monomolecular component. Binary mixtures that contained as little as 1% of the S-, nontarget odorant, however, were sufficiently different perceptually to increase behavioral RTs (i.e., rats hesitated longer before responding); RTs changed systematically as a function of the binary ratio. Interestingly, the rate of RT change was dependent on which odorant served as the S+, suggesting an asymmetric interaction between the 2 odorants. The data demonstrate the value of behavioral RT as a sensitive measure of suprathreshold perceptual responding.
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Affiliation(s)
- Wendy M Yoder
- Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA
| | - Leslie Gaynor
- Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Ethan Windham
- Health Science Program, University of Florida, Gainesville, FL 32611, USA
| | - Michelle Lyman
- Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Olivia Munizza
- Interdisciplinary Studies Major in Neurobiological Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Barry Setlow
- Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA, Department of Psychiatry, University of Florida, Gainesville, FL 32611, USA, Department of Neuroscience, University of Florida, Gainesville, FL 32611, USA and
| | | | - David W Smith
- Program in Behavioral and Cognitive Neuroscience, Department of Psychology, University of Florida, Gainesville, FL 32611, USA, Center for Smell and Taste, University of Florida, Gainesville, FL 32611, USA
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2,4,6-trichloroanisole is a potent suppressor of olfactory signal transduction. Proc Natl Acad Sci U S A 2013; 110:16235-40. [PMID: 24043819 DOI: 10.1073/pnas.1300764110] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We investigated the sensitivity of single olfactory receptor cells to 2,4,6-trichloroanisole (TCA), a compound known for causing cork taint in wines. Such off-flavors have been thought to originate from unpleasant odor qualities evoked by contaminants. However, we here show that TCA attenuates olfactory transduction by suppressing cyclic nucleotide-gated channels, without evoking odorant responses. Surprisingly, suppression was observed even at extremely low (i.e., attomolar) TCA concentrations. The high sensitivity to TCA was associated with temporal integration of the suppression effect. We confirmed that potent suppression by TCA and similar compounds was correlated with their lipophilicity, as quantified by the partition coefficient at octanol/water boundary (pH 7.4), suggesting that channel suppression is mediated by a partitioning of TCA into the lipid bilayer of plasma membranes. The rank order of suppression matched human recognition of off-flavors: TCA equivalent to 2,4,6-tribromoanisole, which is much greater than 2,4,6-trichlorophenol. Furthermore, TCA was detected in a wide variety of foods and beverages surveyed for odor losses. Our findings demonstrate a potential molecular mechanism for the reduction of flavor.
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Osada K, Hanawa M, Tsunoda K, Izumi H. Evaluation of the Masking of Dimethyl Sulfide Odors by Citronellal, Limonene and Citral through the Use of Trained Odor Sensor Mice. Chem Senses 2012; 38:57-65. [DOI: 10.1093/chemse/bjs077] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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28
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Chaput MA, El Mountassir F, Atanasova B, Thomas-Danguin T, Le Bon AM, Perrut A, Ferry B, Duchamp-Viret P. Interactions of odorants with olfactory receptors and receptor neurons match the perceptual dynamics observed for woody and fruity odorant mixtures. Eur J Neurosci 2012; 35:584-97. [PMID: 22304504 DOI: 10.1111/j.1460-9568.2011.07976.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The present study aimed to create a direct bridge between observations on peripheral and central responses to odorant mixtures and their components. Three experiments were performed using mixtures of fruity (isoamyl acetate; ISO) and woody (whiskey lactone; WL) odorants known to contribute to some of the major notes in Burgundy red wine. These experiments consisted of (i) calcium imaging of human embryonic kidney cells (HEK293T) transfected with olfactory receptors (ORs); (ii) single-unit electrophysiological recordings from olfactory receptor neurons (ORNs) and analyses of electro-olfactogram (EOG) responses in the rat nose in vivo; and (iii) psychophysical measurements of the perceived intensity of the mixtures as rated by human subjects. The calcium imaging and electrophysiological results revealed that ISO and WL can act simultaneously on single ORs or ORNs and confirm that receptor responses to mixtures are not the result of a simple sum of the effects of the individual mixture compounds. The addition of WL to ISO principally suppressed the ORN activation induced by ISO alone and was found to enhance this activation in a subset of cases. In the human studies, the addition of high concentrations of WL to ISO decreased the perceived intensity of the ISO. In contrast, the addition of low concentrations of WL enhanced the perceived intensity of the fruity note (ISO) in this mixture, as it enhanced EOG responses in ORNs. Thus, both OR and ORN responses to ISO + WL mixtures faithfully reflected perceptual response changes, so the odour mixture information is set up after the peripheral stage of the olfactory system.
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Affiliation(s)
- M A Chaput
- UMR 5292, Centre de recherche en neurosciences de Lyon, Université de Lyon, CNRS, INSERM, 50 avenue Tony Garnier, F-69366 Lyon, France.
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Kishino Y, Kato H, Kurahashi T, Takeuchi H. Chemical structures of odorants that suppress ion channels in the olfactory receptor cell. J Physiol Sci 2011; 61:231-45. [PMID: 21431980 PMCID: PMC10717247 DOI: 10.1007/s12576-011-0142-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 03/08/2011] [Indexed: 01/30/2023]
Abstract
It has been proposed that odorant suppression of the cyclic nucleotide-gated (CNG) channel is responsible for olfactory masking. In this study, the effect of odorant chain length and functional group on this suppression was investigated. Because similar suppression has been observed for voltage-gated channels also, we used voltage-gated Na channels in the olfactory receptor cell as a tool for substance screening. These features were then re-examined using CNG channels. Interestingly, both CNG and Na channels were suppressed in a similar manner-carboxylic acids had little effect and suppression became stronger when the chain length of the alcohol or ester was increased. Degree of suppression was correlated with the distribution coefficients (Log D), irrespective of the molecules used. Results obtained here may provide information for the development of novel masking agents based on molecular architecture.
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Affiliation(s)
- Yukako Kishino
- Graduate School of Frontier Bioscience, Osaka University, Osaka, 560-8531 Japan
| | - Hiroyuki Kato
- Departments of Chemistry and Materials Science, Graduate School of Science, Osaka City University, Osaka, 558-8585 Japan
| | - Takashi Kurahashi
- Graduate School of Frontier Bioscience, Osaka University, Osaka, 560-8531 Japan
| | - Hiroko Takeuchi
- Graduate School of Frontier Bioscience, Osaka University, Osaka, 560-8531 Japan
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30
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Reisert J. Origin of basal activity in mammalian olfactory receptor neurons. J Gen Physiol 2010; 136:529-40. [PMID: 20974772 PMCID: PMC2964517 DOI: 10.1085/jgp.201010528] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Accepted: 10/01/2010] [Indexed: 01/11/2023] Open
Abstract
Mammalian odorant receptors form a large, diverse group of G protein-coupled receptors that determine the sensitivity and response profile of olfactory receptor neurons. But little is known if odorant receptors control basal and also stimulus-induced cellular properties of olfactory receptor neurons other than ligand specificity. This study demonstrates that different odorant receptors have varying degrees of basal activity, which drives concomitant receptor current fluctuations and basal action potential firing. This basal activity can be suppressed by odorants functioning as inverse agonists. Furthermore, odorant-stimulated olfactory receptor neurons expressing different odorant receptors can have strikingly different response patterns in the later phases of prolonged stimulation. Thus, the influence of odorant receptor choice on response characteristics is much more complex than previously thought, which has important consequences on odor coding and odor information transfer to the brain.
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Affiliation(s)
- Johannes Reisert
- Monell Chemical Senses Center, Philadelphia, PA 19104, USA. jreisert@monell.org
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31
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Osada K, Hanawa M, Tsunoda K, Izumi H. Alteration of mouse urinary odor by ingestion of the xenobiotic monoterpene citronellal. Chem Senses 2010; 36:137-47. [PMID: 20956737 DOI: 10.1093/chemse/bjq104] [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
Body odors provide a rich source of sensory information for other animals. There is considerable evidence to suggest that short-term fluctuations in body odor can be caused by diet; however, few, if any, previous studies have demonstrated that specific compounds can directly mask or alter mouse urinary odor when ingested and thus alter another animal's behavior. To investigate whether the ingestion of citronellal, a monoterpene aldehyde that produces an intense aroma detected by both humans and mice, can alter mouse urinary odor, mice (C57BL6J) were trained in a Y maze to discriminate between the urinary odors of male donor mice that had ingested either citronellal in aqueous solution or a control solution. Trained mice could discriminate between urinary odors from the citronellal ingestion and control groups. A series of generalization tests revealed that citronellal ingestion directly altered mouse urinary odor. Moreover, trained mice that had successfully discriminated between urinary odors from donor mice of different ages failed to detect age-related changes in urine from male mice that had ingested 50 ppm of citronellal. This study is the first to show that ingestion of a xenobiotic can alter mouse urinary odor and confuse the behavioral responses of trained mice to age-related scents.
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Affiliation(s)
- Kazumi Osada
- Department of Oral Physiology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan.
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32
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Hillier NK, Vickers NJ. Mixture interactions in moth olfactory physiology: examining the effects of odorant mixture, concentration, distal stimulation, and antennal nerve transection on sensillar responses. Chem Senses 2010; 36:93-108. [PMID: 20937614 DOI: 10.1093/chemse/bjq102] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The insect olfactory system is challenged to decipher valid signals from among an assortment of chemical cues present in the airborne environment. In the moth, Heliothis virescens, males rely upon detection and discrimination of a unique blend of components in the female sex pheromone to locate mates. The effect of variable odor mixtures was used to examine physiological responses from neurons within sensilla on the moth antenna sensitive to female sex pheromone components. Increasing concentrations of heliothine sex pheromone components applied in concert with the cognate stimulus for each neuronal type resulted in mixture suppression of activity, except for one odorant combination where mixture enhancement was apparent. Olfactory receptor neuron (ORN) responses were compared between moths with intact and transected antennal nerves to determine whether specific instances of suppression might be influenced by central mechanisms. Type A sensilla showed little variation in response between transected and intact preparations; however, recordings from type B sensilla with transected antennal nerves exhibited reduced mixture suppression. Testing by parallel stimulation of distal antennal segments while recording and stimulating proximal segments dismissed the possibility of interneuronal or ephaptic effects upon sensillar responses. The results indicate that increasing concentrations of "noncognate" odorants in an odor mixture or antennal nerve transection can produce variation in the intensity and temporal dynamics of physiological recordings from H. virescens ORNs.
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Affiliation(s)
- N K Hillier
- Department of Biology, Acadia University, Wolfville, Nova Scotia B4P2R6, Canada.
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33
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Abstract
In mammalian species, detection of pheromone cues by the vomeronasal organ (VNO) at different concentrations can elicit distinct behavioral responses and endocrine changes. It is not well understood how concentration-dependent activation of the VNO impacts innate behaviors. In this study, we find that, when mice investigate the urogenital areas of a conspecific animal, the urinary pheromones can reach the VNO at a concentration of approximately 1% of that in urine. At this level, urinary pheromones elicit responses from a subset of cells that are tuned to sex-specific cues and provide unambiguous identification of the sex and strain of animals. In contrast, low concentrations of urine do not activate these cells. Strikingly, we find a population of neurons that is only activated by low concentrations of urine. The properties of these neurons are not found in neurons responding to putative single-compound pheromones. Additional analyses show that these neurons are masked by high-concentration pheromones. Thus, an antagonistic interaction in natural pheromones results in the activation of distinct populations of cells at different concentrations. The differential activation is likely to trigger different downstream circuitry and underlies the concentration-dependent pheromone perception.
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34
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Affiliation(s)
- Barry W Ache
- Center for Smell and Taste, University of Florida, Gainesville, 32610, USA.
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35
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Takeuchi H, Ishida H, Hikichi S, Kurahashi T. Mechanism of olfactory masking in the sensory cilia. J Gen Physiol 2009; 133:583-601. [PMID: 19433623 PMCID: PMC2713142 DOI: 10.1085/jgp.200810085] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 04/22/2009] [Indexed: 12/02/2022] Open
Abstract
Olfactory masking has been used to erase the unpleasant sensation in human cultures for a long period of history. Here, we show a positive correlation between the human masking and the odorant suppression of the transduction current through the cyclic nucleotide-gated (CNG) and Ca2+-activated Cl- (Cl(Ca)) channels. Channels in the olfactory cilia were activated with the cytoplasmic photolysis of caged compounds, and their sensitiveness to odorant suppression was measured with the whole cell patch clamp. When 16 different types of chemicals were applied to cells, cyclic AMP (cAMP)-induced responses (a mixture of CNG and Cl(Ca) currents) were suppressed widely with these substances, but with different sensitivities. Using the same chemicals, in parallel, we measured human olfactory masking with 6-rate scoring tests and saw a correlation coefficient of 0.81 with the channel block. Ringer's solution that was just preexposed to the odorant-containing air affected the cAMP-induced current of the single cell, suggesting that odorant suppression occurs after the evaporation and air/water partition of the odorant chemicals at the olfactory mucus. To investigate the contribution of Cl(Ca), the current was exclusively activated by using the ultraviolet photolysis of caged Ca, DM-nitrophen. With chemical stimuli, it was confirmed that Cl(Ca) channels were less sensitive to the odorant suppression. It is interpreted, however, that in the natural odorant response the Cl(Ca) is affected by the reduction of Ca2+ influx through the CNG channels as a secondary effect. Because the signal transmission between CNG and Cl(Ca) channels includes nonlinear signal-boosting process, CNG channel blockage leads to an amplified reduction in the net current. In addition, we mapped the distribution of the Cl(Ca) channel in living olfactory single cilium using a submicron local [Ca2+]i elevation with the laser photolysis. Cl(Ca) channels are expressed broadly along the cilia. We conclude that odorants regulate CNG level to express masking, and Cl(Ca) in the cilia carries out the signal amplification and reduction evenly spanning the entire cilia. The present findings may serve possible molecular architectures to design effective masking agents, targeting olfactory manipulation at the nano-scale ciliary membrane.
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Affiliation(s)
- Hiroko Takeuchi
- Graduate School of Frontier Biosciences, Osaka University, Osaka 560-8531, Japan
| | - Hirohiko Ishida
- Perfumery Development Research Laboratories, Kao Corporation, Tokyo, 131-8501, Japan
| | - Satoshi Hikichi
- Perfumery Development Research Laboratories, Kao Corporation, Tokyo, 131-8501, Japan
| | - Takashi Kurahashi
- Graduate School of Frontier Biosciences, Osaka University, Osaka 560-8531, Japan
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36
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Abstract
Deciphering olfactory encoding requires a thorough description of the ligands that activate each odorant receptor (OR). In mammalian systems, however, ligands are known for fewer than 50 of more than 1400 human and mouse ORs, greatly limiting our understanding of olfactory coding. We performed high-throughput screening of 93 odorants against 464 ORs expressed in heterologous cells and identified agonists for 52 mouse and 10 human ORs. We used the resulting interaction profiles to develop a predictive model relating physicochemical odorant properties, OR sequences, and their interactions. Our results provide a basis for translating odorants into receptor neuron responses and for unraveling mammalian odor coding.
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Affiliation(s)
- Harumi Saito
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Qiuyi Chi
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Hanyi Zhuang
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Hiro Matsunami
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
- Department of Neurobiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Joel D. Mainland
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
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37
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Kleene SJ. The electrochemical basis of odor transduction in vertebrate olfactory cilia. Chem Senses 2008; 33:839-59. [PMID: 18703537 DOI: 10.1093/chemse/bjn048] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Most vertebrate olfactory receptor neurons share a common G-protein-coupled pathway for transducing the binding of odorant into depolarization. The depolarization involves 2 currents: an influx of cations (including Ca2+) through cyclic nucleotide-gated channels and a secondary efflux of Cl- through Ca2+-gated Cl- channels. The relation between stimulus strength and receptor current shows positive cooperativity that is attributed to the channel properties. This cooperativity amplifies the responses to sufficiently strong stimuli but reduces sensitivity and dynamic range. The odor response is transient, and prolonged or repeated stimulation causes adaptation and desensitization. At least 10 mechanisms may contribute to termination of the response; several of these result from an increase in intraciliary Ca2+. It is not known to what extent regulation of ionic concentrations in the cilium depends on the dendrite and soma. Although many of the major mechanisms have been identified, odor transduction is not well understood at a quantitative level.
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Affiliation(s)
- Steven J Kleene
- Department of Cancer and Cell Biology, University of Cincinnati, PO Box 670667, 231 Albert Sabin Way, Cincinnati, OH 45267-0667, USA.
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38
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Barbour J, Neuhaus EM, Piechura H, Stoepel N, Mashukova A, Brunert D, Sitek B, Stühler K, Meyer HE, Hatt H, Warscheid B. New insight into stimulus-induced plasticity of the olfactory epithelium in Mus musculus by quantitative proteomics. J Proteome Res 2008; 7:1594-605. [PMID: 18336002 DOI: 10.1021/pr7005796] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The olfactory system is exposed to a plethora of chemical compounds throughout an organism's lifespan. Anticipation of stimuli and construction of appropriate neural filters present a significant challenge. This may be addressed via modulation of the protein composition of the sensory epithelium in response to environmental conditions. To reveal the mechanisms governing these changes, we employed a comprehensive quantitative proteomics strategy. Two groups of juvenile mice were treated with either pulsed or continuous application of octanal. After 20 days of treatment, we performed a behavioral study and conducted electrophysiological recordings from the olfactory epithelium (OE). Both treated groups demonstrated peripheral desensitization to octanal; however, only the 'continuous' group exhibited habituation. To obtain novel insight into the molecular mechanisms underpinning the peripheral desensitization to octanal, the OE proteomes of octanal-treated mice versus control were quantitatively analyzed using two-dimensional difference gel electrophoresis. We identified several significantly regulated proteins that were functionally classified as calcium-binding proteins, cytoskeletal proteins, and lipocalins. The calcium-binding proteins and cytoskeletal proteins were up-regulated in the 'pulsed' group, whereas in the 'continuous' group, four lipocalins were significantly down-regulated. Uniquely, the lipocalin odorant-binding protein Ia was drastically down-regulated in both groups. The identified proteins reflect changes throughout the entire OE, corresponding to changes in neuronal, non-neuronal, and pericellular processes. We report the regulation of several promising candidates for the investigation of odorant-induced changes of the OE. Among these proteins are different lipocalins, which seem to play a crucial role in the regulation of the sensitivity of the olfactory system.
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Affiliation(s)
- Jon Barbour
- Medizinisches Proteom-Center, Ruhr-University Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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Chen TY, Takeuchi H, Kurahashi T. Odorant inhibition of the olfactory cyclic nucleotide-gated channel with a native molecular assembly. ACTA ACUST UNITED AC 2006; 128:365-71. [PMID: 16940558 PMCID: PMC2151561 DOI: 10.1085/jgp.200609577] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human olfaction comprises the opposing actions of excitation and inhibition triggered by odorant molecules. In olfactory receptor neurons, odorant molecules not only trigger a G-protein–coupled signaling cascade but also generate various mechanisms to fine tune the odorant-induced current, including a low-selective odorant inhibition of the olfactory signal. This wide-range olfactory inhibition has been suggested to be at the level of ion channels, but definitive evidence is not available. Here, we report that the cyclic nucleotide-gated (CNG) cation channel, which is a key element that converts odorant stimuli into electrical signals, is inhibited by structurally unrelated odorants, consistent with the expression of wide-range olfactory inhibition. Interestingly, the inhibitory effect was small in the homo-oligomeric CNG channel composed only of the principal channel subunit, CNGA2, but became larger in channels consisting of multiple types of subunits. However, even in the channel containing all native subunits, the potency of the suppression on the cloned CNG channel appeared to be smaller than that previously shown in native olfactory neurons. Nonetheless, our results further showed that odorant suppressions are small in native neurons if the subsequent molecular steps mediated by Ca2+ are removed. Thus, the present work also suggests that CNG channels switch on and off the olfactory signaling pathway, and that the on and off signals may both be amplified by the subsequent olfactory signaling steps.
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Affiliation(s)
- Tsung-Yu Chen
- Center for Neuroscience and Department of Neurology, University of California, Davis, CA 95616, USA.
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40
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Schmachtenberg O. Histological and electrophysiological properties of crypt cells from the olfactory epithelium of the marine teleost Trachurus symmetricus. J Comp Neurol 2006; 495:113-21. [PMID: 16432906 DOI: 10.1002/cne.20847] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Crypt cells from the olfactory epithelium of the Pacific jack mackerel Trachurus symmetricus were characterized by light and electron microscopy and analyzed in dissociation with the patch-clamp technique in its cell-attached, perforated patch and normal whole-cell mode. Isolated crypt cells remained united with their supporting cells, and both were electrically coupled through gap junctions. Under voltage-clamp, depolarizing voltage steps triggered a transient sodium current, a sustained calcium current, and two types of potassium currents with fast and slow inactivation kinetics. No calcium-dependent potassium current could be observed. The sodium current was blocked by saxitoxin, the calcium current by cobalt and furnidipine, and the potassium currents by tetraethylammonium chloride. In the cell-attached configuration, crypt cells displayed spontaneous spike activity and responded to amino acid solutions with dose-dependent excitation, followed by a period of spike inhibition. These first recordings of individual crypt cells provide the basis for future studies of their odorant specificity, transduction mechanism, and overall function in the fish olfactory epithelium.
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Affiliation(s)
- Oliver Schmachtenberg
- Centro de Neurociencias de Valparaiso CNV, Facultad de Ciencias, Universidad de Valparaiso, Valparaiso, Chile.
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41
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Schmachtenberg O, Bacigalupo J. Olfactory transduction in ciliated receptor neurons of the Cabinza grunt, Isacia conceptionis (Teleostei: Haemulidae). Eur J Neurosci 2005; 20:3378-86. [PMID: 15610170 DOI: 10.1111/j.1460-9568.2004.03825.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The ciliated receptor neurons of fish olfactory organs are thought to transduce amino acids through a cAMP-dependent transduction pathway, but direct physiological evidence for this hypothesis remains scarce and is confined to catfish and trout. We investigated olfactory transduction in a marine fish, the Cabinza grunt Isacia conceptionis (Perciformes, Teleostei). The olfactory epithelium was characterized using light and electron microscopy, and isolated ciliated receptor neurons were recorded with the perforated patch-clamp technique. Cells were stimulated with puffer pipettes containing amino acid odourants, IBMX plus forskolin or 8 bromo-cAMP. All three stimuli triggered transient inward currents at a holding potential of -70 mV and responses with outward-rectifying current-voltage relationships. The characteristics of the transduction currents induced by each stimulus were similar across cells and indistinguishable within the same cell, supporting the hypothesis of a cAMP pathway mediating transduction of amino acids in ciliated olfactory receptor neurons.
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Affiliation(s)
- Oliver Schmachtenberg
- Centro de Neurociencias de Valparaiso, Facultad de Ciencias, Universidad de Valparaiso, Avda. Gran Bretania 1111, Playa Ancha, Valparaiso, Chile.
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42
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Duchamp-Viret P, Duchamp A, Chaput MA. Single olfactory sensory neurons simultaneously integrate the components of an odour mixture. Eur J Neurosci 2004; 18:2690-6. [PMID: 14656317 DOI: 10.1111/j.1460-9568.2003.03001.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Most odours are complex mixtures. However, the capacities of olfactory sensory neurons (OSNs) to process complex odour stimuli have never been explored in air-breathing vertebrates. To face this issue, the present study compares the electrical responses of single OSNs to two odour molecules, delivered singly and mixed together, in rats in vivo. This work is the first aimed at demonstrating that single OSNs simultaneously integrate several chemical signals and which, furthermore, attempts to describe such processes for the whole concentration range over which single OSNs can work. The results stress that complex interactions occur between components in odour mixtures and that OSN responses to such mixtures are not simply predictable from the responses to their components. Three types of interactions are described. They are termed suppression, hypoadditivity and synergy, in accord with psychophysical terminology. This allows us to draw links between peripheral odour reception and central odour coding. Indeed, events occurring in single OSNs may account for the dominating or even the masking effects of odour molecules in complex mixtures, i.e. for the prevailing action of a minor component in the final qualitative perception of a mixture. We conclude that our observations with binary mixtures anticipate the complexity of processes which may rise at the level of a single OSN in physiological conditions. Following this hypothesis, a natural odour would induce a multi-chemical integration at the level of single OSNs which may result in refining their individual odour-coding properties, leading them to play a crucial role in the final performance of the olfactory system.
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Affiliation(s)
- Patricia Duchamp-Viret
- Laboratoire de Neurosciences et Systèmes Sensoriels, CNRS, UMR 5020, Université Claude Bernard, 50 avenue Tony Garnier, 69366 Lyon cedex 07, France.
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Oka Y, Omura M, Kataoka H, Touhara K. Olfactory receptor antagonism between odorants. EMBO J 2003; 23:120-6. [PMID: 14685265 PMCID: PMC1271670 DOI: 10.1038/sj.emboj.7600032] [Citation(s) in RCA: 207] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Accepted: 11/24/2003] [Indexed: 01/31/2023] Open
Abstract
The detection of thousands of volatile odorants is mediated by several hundreds of different G protein-coupled olfactory receptors (ORs). The main strategy in encoding odorant identities is a combinatorial receptor code scheme in that different odorants are recognized by different sets of ORs. Despite increasing information on agonist-OR combinations, little is known about the antagonism of ORs in the mammalian olfactory system. Here we show that odorants inhibit odorant responses of OR(s), evidence of antagonism between odorants at the receptor level. The antagonism was demonstrated in a heterologous OR-expression system and in single olfactory neurons that expressed a given OR, and was also visualized at the level of the olfactory epithelium. Dual functions of odorants as an agonist and an antagonist to ORs indicate a new aspect in the receptor code determination for odorant mixtures that often give rise to novel perceptual qualities that are not present in each component. The current study also provides insight into strategies to modulate perceived odorant quality.
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Affiliation(s)
- Yuki Oka
- Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan
| | - Masayo Omura
- Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan
| | - Hiroshi Kataoka
- Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan
| | - Kazushige Touhara
- Department of Integrated Biosciences, The University of Tokyo, Chiba, Japan
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8562, Japan. Tel.: +81 471 36 3624; Fax: +81 471 36 3626; E-mail:
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44
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Takeuchi H, Kurahashi T. Identification of second messenger mediating signal transduction in the olfactory receptor cell. J Gen Physiol 2003; 122:557-67. [PMID: 14581582 PMCID: PMC2229575 DOI: 10.1085/jgp.200308911] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2003] [Accepted: 09/22/2003] [Indexed: 12/30/2022] Open
Abstract
One of the biggest controversial issues in the research of olfaction has been the mechanism underlying response generation to odorants that have been shown to fail to produce cAMP when tested by biochemical assays with olfactory ciliary preparations. Such observations are actually the original source proposing a possibility for the presence of multiple and parallel transduction pathways. In this study the activity of transduction channels in the olfactory cilia was recorded in cells that retained their abilities of responding to odorants that have been reported to produce InsP3 (instead of producing cAMP, and therefore tentatively termed "InsP3 odorants"). At the same time, the cytoplasmic cNMP concentration ([cNMP]i) was manipulated through the photolysis of caged compounds to examine their real-time interactions with odorant responses. Properties of responses induced by both InsP3 odorants and cytoplasmic cNMP resembled each other in their unique characteristics. Reversal potentials of currents were 2 mV for InsP3 odorant responses and 3 mV for responses induced by cNMP. Current and voltage (I-V) relations showed slight outward rectification. Both responses showed voltage-dependent adaptation when examined with double pulse protocols. When brief pulses of the InsP3 odorant and cytoplasmic cNMP were applied alternatively, responses expressed cross-adaptation with each other. Furthermore, both responses were additive in a manner as predicted quantitatively by the theory that signal transduction is mediated by the increase in cytoplasmic cAMP. With InsP3 odorants, actually, remarkable responses could be detected in a small fraction of cells ( approximately 2%), explaining the observation for a small production of cAMP in ciliary preparations obtained from the entire epithelium. The data will provide evidence showing that olfactory response generation and adaptation are regulated by a uniform mechanism for a wide variety of odorants.
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Affiliation(s)
- Hiroko Takeuchi
- Department of Frontier Biosciences, Osaka University, Toyonaka, Osaka 560-8531, Japan.
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Casaña-Giner V, Levi V, Navarro-Llopis V, Jang EB. Implication of SAR of male medfly attractants in insect olfaction. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2002; 13:629-640. [PMID: 12570041 DOI: 10.1080/1062936021000043382] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Medfly (Ceratitis capitata) males are strongly attracted by different compounds, not described as pheromones. The best attractants reported are (+)-alpha-copaene, a sesquiterpene of natural source and (-)-ceralure-B1, a non-natural iodinated cyclohexane ester. Although their origin, atomic composition, chemical and physical properties are rather different, they show similar attraction to medflies. The question of why these compounds, act behaviorally in the same way, has been never addressed in research papers. We show here for the first time that these compounds have quite similar stereochemistry, water accessible surfaces, certain local dipole moments and, to some extent, similar octanol/water partition coefficient (log P). When seven carbons, one oxygen and one iodine belonging to (-)-ceralure-B1 are selectively chosen based on topological homology with (+)-alpha-copaene and are overlaid with nine corresponding carbons of (+)-alpha-copaene, the RMS is 0.367 A. This represents a high degree of steric resemblance. Local dipole moments and charges are similar in those regions where the molecules show topological homologies. Thus, we hypothesize that these two molecules could interact with the same male medfly's odorant receptor(s). The implications of this result in future research in insect olfaction is discussed.
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Affiliation(s)
- V Casaña-Giner
- Centro de Ecología Química Agricola, Universidad Politécnica de Valencia, Edif. 9B (1-4), Lab. 111, Cami de Vera s/n, Valencia 46071, Spain.
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Laing DG, Link C, Jinks AL, Hutchinson I. The limited capacity of humans to identify the components of taste mixtures and taste-odour mixtures. Perception 2002; 31:617-35. [PMID: 12044101 DOI: 10.1068/p3205] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The capacity of humans to identify the components of taste mixtures and odour-taste mixtures was investigated in two experiments. Subjects were trained to identify the components presented alone and to use a 'yes/no' procedure to identify them in mixtures. All stimuli were presented with a retronasal (by mouth) technique. A maximum of three tastants were identified in both types of mixtures, only one tastant was identified in five-component taste mixtures, and no component was identified in four-component odour-taste mixtures. Importantly, in no instance was the olfactory stimulus identified in any mixture with tastes, including binary mixtures. Loss of identity of the odorant in binary and ternary mixtures may have been due to suppression as a consequence of temporal processing, or to the absence of an association between the odorant and tastants that had established an identifiable percept. In contrast, poor identification of the components of the quaternary odour-taste mixture and quinternary taste mixture is attributed to the limited capacity of working memory. Overall, the poorer ability to identify components in odour-taste mixtures than in taste mixtures indicates that interactions occurred between the two senses, challenging the proposal that odours and tastes are processed independently when present in complex chemosensory stimuli.
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Affiliation(s)
- David G Laing
- Centre For Advanced Food Research, University of Western Sydney, Richmond, NSW, Australia.
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Carlsson MA, Hansson BS. Responses in highly selective sensory neurons to blends of pheromone components in the moth Agrotis segetum. JOURNAL OF INSECT PHYSIOLOGY 2002; 48:443-451. [PMID: 12770093 DOI: 10.1016/s0022-1910(02)00065-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Pheromone detecting sensory neurons in moths are known to be highly sensitive and selective. Female-emitted sexual pheromones are normally mixtures of a few to several components. However, not much is known about how receptor neurons respond to blends of compounds. In the present study we investigated how four physiological types of pheromone component-selective neurons responded to binary mixtures or to the complete blend in the turnip moth Agrotis segetum. We found that responses to mixtures only rarely differed from that to the excitatory component alone. The mixture interactions were exclusively suppressive and occurred only at high concentrations. Therefore we conclude that the, in A. segetum, commonly observed mixture interactions observed in higher brain centra are mainly the result of central nervous processing and that information about the pheromone components reaches the antennal lobes virtually unaltered. In addition, we found a physiological type of receptor neuron, responding selectively to one of the female-emitted pheromone components, that has previously not been observed in the Swedish population.
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Affiliation(s)
- Mikael A. Carlsson
- Department of Crop Science, Chemical Ecology, Swedish University of Agricultural Sciences, P.O. Box 44, SE-230 53, Alnarp, Sweden
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48
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Spehr M, Wetzel CH, Hatt H, Ache BW. 3-phosphoinositides modulate cyclic nucleotide signaling in olfactory receptor neurons. Neuron 2002; 33:731-9. [PMID: 11879650 DOI: 10.1016/s0896-6273(02)00610-4] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Phosphatidylinositol 3-kinase (PI3K)-dependent phosphoinositide signaling has been implicated in diverse cellular systems coupled to receptors for many different ligands, but the extent to which it functions in sensory transduction is yet to be determined. We now report that blocking PI3K activity increases odorant-evoked, cyclic nucleotide-dependent elevation of [Ca(2+)](i) in acutely dissociated rat olfactory receptor neurons and does so in an odorant-specific manner. These findings imply that 3-phosphoinositide signaling acts in vertebrate olfactory transduction to inhibit cyclic nucleotide-dependent excitation of the cells and that the interaction of the two signaling pathways is important in odorant coding, indicating that 3-phosphoinositide signaling can play a role in sensory transduction.
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Affiliation(s)
- Marc Spehr
- Department of Cell Physiology, Ruhr University Bochum, Bochum, Germany
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49
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Wetzel CH, Spehr M, Hatt H. Phosphorylation of voltage-gated ion channels in rat olfactory receptor neurons. Eur J Neurosci 2001; 14:1056-64. [PMID: 11683897 DOI: 10.1046/j.0953-816x.2001.01722.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In olfactory receptor neurons (ORNs), ligand-odorant receptor interactions cause G protein-mediated activation of adenylate cyclase and a subsequent increase in concentration of the intracellular messenger cAMP. Odorant-evoked elevation in cAMP is thought to directly activate a cation-selective cyclic nucleotide-gated channel, which causes external Ca2+ influx, leading to membrane depolarization and the generation of action potentials. Our data show that in freshly dissociated rat ORNs, odorant-induced elevation in cAMP also activates cAMP-dependent protein kinase (PKA), which is then able to phosphorylate various protein targets in the olfactory signal transduction pathway, specifically voltage-gated sodium and calcium channels. The presence of PKI (PKA inhibitor peptide) blocked the modulatory action of cAMP on voltage-gated ion channels. By modulating the input/output properties of the sensory neurons, this mechanism could take part in the complex adaptation process in odorant perception. In addition, we found modulation of voltage-gated sodium and calcium channel currents by 5-hydroxytryptamine and the dopamine D1 receptor agonist SKF 38393. These findings suggest that in situ ORNs might also be a target for efferent modulation.
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Affiliation(s)
- C H Wetzel
- Department of Cell Physiology, Ruhr-University Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany
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Yee KK, Wysocki CJ. Odorant exposure increases olfactory sensitivity: olfactory epithelium is implicated. Physiol Behav 2001; 72:705-11. [PMID: 11337002 DOI: 10.1016/s0031-9384(01)00428-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Exposure-induced shifts in sensitivity to odors may involve peripheral and/or central components of the olfactory system. The ability to disconnect the olfactory epithelium from the bulbs provides a unique opportunity to examine how odorant exposure affects each component. In one experiment, odor thresholds were established for either amyl acetate or androstenone. The mice were then exposed for 10 days to the same test odorant for which a threshold was obtained. After exposure, sensitivity to the odorant increased relative to preexposure levels. The mice then underwent bilateral olfactory nerve transection (BNX). When both groups of mice were tested 45-50 days after recovery from surgery and return of olfactory function, increased sensitivity to the exposed odorant persisted; however, 121-203 days after surgery, sensitivity returned to preexposure levels. Another experiment was similar to the first except that mice were exposed to an odorant, either amyl acetate or androstenone, for 10 days beginning 1 day after BNX or sham surgery. When the mice were tested 45-50 days after surgery, sensitivity to the exposed odorant was increased relative to preexposure levels, whereas sensitivity to the nonexposed odorant remained at preexposure levels. Although further work is needed to determine the precise mechanism(s) underlying shifts in sensitivity to odors, these studies provide additional evidence for peripheral involvement in exposure-induced sensitization to odorants and demonstrate the remarkable capacity of the olfactory system to maintain or even regain sensitivity after injury.
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Affiliation(s)
- K K Yee
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104-3308, USA.
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