scholarly journals Ca2+-activated Cl current predominates in threshold response of mouse olfactory receptor neurons

2018 ◽  
Vol 115 (21) ◽  
pp. 5570-5575 ◽  
Author(s):  
Rong-Chang Li ◽  
Chih-Chun Lin ◽  
Xiaozhi Ren ◽  
Jingjing Sherry Wu ◽  
Laurie L. Molday ◽  
...  
Keyword(s):  
Olfactory Receptor ◽  
Signal Amplification ◽  
Olfactory Receptor Neurons ◽  
Behavioral Threshold ◽  
Olfactory Transduction ◽  
Threshold Response ◽  
Axonal Projections ◽  
Cl Channels ◽  
Receptor Neurons ◽  
The Brain

In mammalian olfactory transduction, odorants activate a cAMP-mediated signaling pathway that leads to the opening of cyclic nucleotide-gated (CNG), nonselective cation channels and depolarization. The Ca2+ influx through open CNG channels triggers an inward current through Ca2+-activated Cl channels (ANO2), which is expected to produce signal amplification. However, a study on an Ano2−/− mouse line reported no elevation in the behavioral threshold of odorant detection compared with wild type (WT). Subsequent studies by others on the same Ano2−/− line, nonetheless, found subtle defects in olfactory behavior and some abnormal axonal projections from the olfactory receptor neurons (ORNs) to the olfactory bulb. As such, the question regarding signal amplification by the Cl current in WT mouse remains unsettled. Recently, with suction-pipette recording, we have successfully separated in frog ORNs the CNG and Cl currents during olfactory transduction and found the Cl current to predominate in the response down to the threshold of action-potential signaling to the brain. For better comparison with the mouse data by others, we have now carried out similar current-separation experiments on mouse ORNs. We found that the Cl current clearly also predominated in the mouse olfactory response at signaling threshold, accounting for ∼80% of the response. In the absence of the Cl current, we expect the threshold stimulus to increase by approximately sevenfold.

scholarly journals Cyclic-nucleotide–gated cation current and Ca2+-activated Cl current elicited by odorant in vertebrate olfactory receptor neurons

2016 ◽  
Vol 113 (40) ◽  
pp. 11078-11087 ◽  
Author(s):  
Rong-Chang Li ◽  
Yair Ben-Chaim ◽  
King-Wai Yau ◽  
Chih-Chun Lin
Keyword(s):  
Cyclic Nucleotide ◽  
Olfactory Receptor ◽  
Signal Amplification ◽  
Time Course ◽  
Olfactory Receptor Neurons ◽  
Cation Current ◽  
Nonselective Cation Channels ◽  
Predominant Component ◽  
Receptor Neurons ◽  
The Brain

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.

scholarly journals Adaptive integrate-and-fire model reproduces the dynamics of olfactory receptor neuron responses in a moth

2019 ◽  
Vol 16 (157) ◽  
pp. 20190246 ◽  
Author(s):  
Marie Levakova ◽  
Lubomir Kostal ◽  
Christelle Monsempès ◽  
Philippe Lucas ◽  
Ryota Kobayashi
Keyword(s):  
Olfactory Receptor ◽  
Time Course ◽  
Olfactory Receptor Neuron ◽  
Receptor Activation ◽  
Olfactory Receptor Neurons ◽  
Response Dynamics ◽  
Spike Threshold ◽  
Olfactory Stimuli ◽  
Receptor Neurons ◽  
The Brain

In order to understand how olfactory stimuli are encoded and processed in the brain, it is important to build a computational model for olfactory receptor neurons (ORNs). Here, we present a simple and reliable mathematical model of a moth ORN generating spikes. The model incorporates a simplified description of the chemical kinetics leading to olfactory receptor activation and action potential generation. We show that an adaptive spike threshold regulated by prior spike history is an effective mechanism for reproducing the typical phasic–tonic time course of ORN responses. Our model reproduces the response dynamics of individual neurons to a fluctuating stimulus that approximates odorant fluctuations in nature. The parameters of the spike threshold are essential for reproducing the response heterogeneity in ORNs. The model provides a valuable tool for efficient simulations of olfactory circuits.

scholarly journals Comparison of the Nasal Olfactory Organs of Various Species of Lizardfishes (Teleostei: Aulopiformes: Synodontidae) with Additional Remarks on the Brain

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
L. Fishelson ◽  
D. Golani ◽  
B. Galil ◽  
M. Goren
Keyword(s):  
Olfactory Epithelium ◽  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Adult Fish ◽  
Supporting Cells ◽  
Receptor Neurons ◽  
Olfactory Organs ◽  
Species Specific ◽  
The Brain

The olfactory organs of lizardfishes (Synodontidae) are situated in two capsules connected to the outside by incurrent and excurrent openings. The olfactory epithelium is in form of petal rosettes each composed of lamellae and a rephe, and bear olfactory receptor neurons, supporting cells and cells with kinocillia. The dimension of rosettes and lamellae, as well as the number of lamellae, increase with growth of the fish; until in adult fish these parameters remaine constant, species specific. In adultSynodusspp. andTrachinocephalus myopsthe rosettes are 3.5–4.0 mm long, with 5–8 lamellae, whereas inSauridaspp. they are 8.0 mm and possess up tp 22 lamellae. The number of ORN ranges from 2,600 on the smaller lamellae to 20,000 on the largest ones. The number of ORN/m of olfactory is ca. 30,000 inSauridaspp. Thus the rosettes ofS. macrolepiswith 20 lamellae possess a total of ca. 170,000 ORN, whereas those ofSy. variegatusandT. myopswith the average of six lamellae possess only ca. 50,000–65,000 ORN. The olfactory nerves lead from the rosettes to the olfactory balbs situated on the olfactory lobes. The differences among the species in olfactory organs are discussed in correlation with their distribution.

scholarly journals The Ca-activated Cl Channel and its Control in Rat Olfactory Receptor Neurons

2003 ◽  
Vol 122 (3) ◽  
pp. 349-364 ◽  
Author(s):  
Johannes Reisert ◽  
Paul J. Bauer ◽  
King-Wai Yau ◽  
Stephan Frings
Keyword(s):  
Diffusion Coefficient ◽  
Olfactory Receptor ◽  
Divalent Cations ◽  
Low Noise ◽  
Sensory Transduction ◽  
Olfactory Receptor Neurons ◽  
Cl Channel ◽  
Cl Channels ◽  
Receptor Neurons ◽  
Transduction Signal

Odorants activate sensory transduction in olfactory receptor neurons (ORNs) via a cAMP-signaling cascade, which results in the opening of nonselective, cyclic nucleotide–gated (CNG) channels. The consequent Ca2+ influx through CNG channels activates Cl channels, which serve to amplify the transduction signal. We investigate here some general properties of this Ca-activated Cl channel in rat, as well as its functional interplay with the CNG channel, by using inside-out membrane patches excised from ORN dendritic knobs/cilia. At physiological concentrations of external divalent cations, the maximally activated Cl current was ∼30 times as large as the CNG current. The Cl channels on an excised patch could be activated by Ca2+ flux through the CNG channels opened by cAMP. The magnitude of the Cl current depended on the strength of Ca buffering in the bath solution, suggesting that the CNG and Cl channels were probably not organized as constituents of a local transducisome complex. Likewise, Cl channels and the Na/Ca exchanger, which extrudes Ca2+, appear to be spatially segregated. Based on the theory of buffered Ca2+ diffusion, we determined the Ca2+ diffusion coefficient and calculated that the CNG and Cl channel densities on the membrane were ∼8 and 62 μm−2, respectively. These densities, together with the Ca2+ diffusion coefficient, demonstrate that a given Cl channel is activated by Ca2+ originating from multiple CNG channels, thus allowing low-noise amplification of the olfactory receptor current.

scholarly journals Olfactory dysfunction in coronavirus disease

2021 ◽  
pp. 94-102
Author(s):  
Aleksandra V. Tsepkolenko ◽  
Sergey M. Pukhlik
Keyword(s):  
Olfactory Receptor ◽  
Clinical Symptoms ◽  
Nasal Congestion ◽  
Specific Treatment ◽  
Olfactory Dysfunction ◽  
Olfactory Receptor Neurons ◽  
Supporting Cells ◽  
Receptor Neurons ◽  
The Brain

Olfactory dysfunction may be the only early clinical manifestation in COVID-19 patients with no other significant signs. It is typical of the disease and can be significant for testing. The purpose of the review is to provide guidance to the otorhinolaryngologist in the problem of olfactory dysfunction in SARS-CoV-2 infection. Materials and Methods: The authors analyzed the available clinical data on the problem of olfactory dysfunction in SARS-CoV-2 infection. The data of statistics, clinical symptoms and pathogenesis were studied. Toexplain anosmia in COVID-19 patients, 4 possible mechanisms are considered: nasal congestion / nasal congestion and rhinorrhea; death of olfactory receptor neurons; infiltration of the brain and damage to the olfactorycenters; damage to the supporting cells of the olfactory epithelium. The analysis of clinical cases of patients with prolonged ansomia against the background of COVID-19 was carried out. Conclusions: Smell after COVID-19 in most cases is restored without specific treatment. There are no reports of studies in patients with long-term anosmia.

scholarly journals Coordinating Receptor Expression and Wiring Specificity in Olfactory Receptor Neurons

2019 ◽  
Author(s):  
Hongjie Li ◽  
Tongchao Li ◽  
Felix Horns ◽  
Jiefu Li ◽  
Qijing Xie ◽  
...  
Keyword(s):  
Olfactory Receptor ◽  
Olfactory Receptors ◽  
Receptor Expression ◽  
Olfactory Receptor Neurons ◽  
Unique Combination ◽  
Axon Targeting ◽  
Transcriptional Regulatory ◽  
Receptor Neurons ◽  
Transcriptional Regulatory Mechanisms ◽  
The Brain

The ultimate function of a neuron is determined by both its physiology and connectivity, but the transcriptional regulatory mechanisms that coordinate these two features are not well understood1–4. The Drosophila Olfactory receptor neurons (ORNs) provide an excellent system to investigate this question. As in mammals5, each Drosophila ORN class is defined by the expression of a single olfactory receptor or a unique combination thereof, which determines their odor responses, and by the single glomerulus to which their axons target, which determines how sensory signals are represented in the brain6–10. In mammals, the coordination of olfactory receptor expression and wiring specificity is accomplished in part by olfactory receptors themselves regulating ORN wiring specificity11–13. However, Drosophila olfactory receptors do not instruct axon targeting6, 14, raising the question as to how receptor expression and wiring specificity are coordinated. Using single-cell RNA-sequencing and genetic analysis, we identified 33 transcriptomic clusters for fly ORNs. We unambiguously mapped 17 to glomerular classes, demonstrating that transcriptomic clusters correspond well with anatomically and physiologically defined ORN classes. We found that each ORN expresses ~150 transcription factors (TFs), and identified a master TF that regulates both olfactory receptor expression and wiring specificity. A second TF plays distinct roles, regulating only receptor expression in one class and only wiring in another. Thus, fly ORNs utilize diverse transcriptional strategies to coordinate physiology and connectivity.

scholarly journals Ca2+-activated Cl− current ensures robust and reliable signal amplification in vertebrate olfactory receptor neurons

2018 ◽  
Vol 116 (3) ◽  
pp. 1053-1058 ◽  
Author(s):  
Johannes Reisert ◽  
Jürgen Reingruber
Keyword(s):  
Olfactory Receptor ◽  
Signal Amplification ◽  
Olfactory Receptor Neuron ◽  
Olfactory Receptor Neurons ◽  
Ion Concentration ◽  
Modeling And Simulations ◽  
Small Space ◽  
Receptor Neurons ◽  
Concentration Changes ◽  
Transduction Current

Activation of most primary sensory neurons results in transduction currents that are carried by cations. One notable exception is the vertebrate olfactory receptor neuron (ORN), where the transduction current is carried largely by the anion Cl−. However, it remains unclear why ORNs use an anionic current for signal amplification. We have sought to provide clarification on this topic by studying the so far neglected dynamics of Na+, Ca2+, K+, and Cl− in the small space of olfactory cilia during an odorant response. Using computational modeling and simulations we compared the outcomes of signal amplification based on either Cl− or Na+ currents. We found that amplification produced by Na+ influx instead of a Cl− efflux is problematic for several reasons: First, the Na+ current amplitude varies greatly, depending on mucosal ion concentration changes. Second, a Na+ current leads to a large increase in the ciliary Na+ concentration during an odorant response. This increase inhibits and even reverses Ca2+ clearance by Na+/Ca2+/K+ exchange, which is essential for response termination. Finally, a Na+ current increases the ciliary osmotic pressure, which could cause swelling to damage the cilia. By contrast, a transduction pathway based on Cl− efflux circumvents these problems and renders the odorant response robust and reliable.

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