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Mechanism of olfactory masking in the sensory cilia.

Takeuchi H, Ishida H, Hikichi S, Kurahashi T - J. Gen. Physiol. (2009)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Frontier Biosciences, Osaka University, Osaka 560-8531, Japan.

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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Spatial distribution of [Ca]i sensitivity along the single cilium. (A) Fluorescent image of a single cilium and the locations of the UV laser stimuli. Stimulus intensity is depicted as a color scaling that is independently shown with a scale bar (top left column; for detail, see Takeuchi and Kurahashi, 2008). (B–G) Waveforms of the current induced by the local laser irradiation. Cell was loaded with 10 mM of caged Ca. All ROIs were circular, and diameters were 1 µm (25 pixels) for filled squares or 0.52 µm (13 pixels) for filled circles. Vh, −50 mV. 100× lens. Laser wavelength, 351 and 364 nm. Output, 70%; transmission, 100%. Data were obtained from points indicated in A. Downward transients observed immediately before the responses are artifacts caused by the trigger signals to initiate the raster scan on LSM. (H) Relation between the distance from the knob and local current responses from eight cells. 100× lens. The lowest horizontal color bars indicate the length of the cilia of corresponding colored plots.
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fig10: Spatial distribution of [Ca]i sensitivity along the single cilium. (A) Fluorescent image of a single cilium and the locations of the UV laser stimuli. Stimulus intensity is depicted as a color scaling that is independently shown with a scale bar (top left column; for detail, see Takeuchi and Kurahashi, 2008). (B–G) Waveforms of the current induced by the local laser irradiation. Cell was loaded with 10 mM of caged Ca. All ROIs were circular, and diameters were 1 µm (25 pixels) for filled squares or 0.52 µm (13 pixels) for filled circles. Vh, −50 mV. 100× lens. Laser wavelength, 351 and 364 nm. Output, 70%; transmission, 100%. Data were obtained from points indicated in A. Downward transients observed immediately before the responses are artifacts caused by the trigger signals to initiate the raster scan on LSM. (H) Relation between the distance from the knob and local current responses from eight cells. 100× lens. The lowest horizontal color bars indicate the length of the cilia of corresponding colored plots.

Mentions: In the experiments of Fig. 10 (local photolysis), a laser-scanning confocal microscope (LSM510; Carl Zeiss, Inc.) equipped with an acousto-optic tunable filter for the laser control was used with a Fluar (DIC) 100×/1.45 NA (oil-immersion) objective lens. The UV laser beam (80 mW: argon laser λ = 351, 364 nm; Coherent) of Zeiss LSM equipped with the region of interest (ROI) function was applied locally to the cilium for photolysis. Argon laser λ = 458 nm was used for visualizing the fluorescence emitted from Lucifer yellow incorporated into the cell via a WC patch pipette, and λ = 488 nm was used for detecting the timing of laser stimulus. The 458- or 488-nm laser beam alone did not cause photolysis when examined with cells. The timing of the light pulse is shown above the current traces in the figures as a downward deflection of the trace.


Mechanism of olfactory masking in the sensory cilia.

Takeuchi H, Ishida H, Hikichi S, Kurahashi T - J. Gen. Physiol. (2009)

Spatial distribution of [Ca]i sensitivity along the single cilium. (A) Fluorescent image of a single cilium and the locations of the UV laser stimuli. Stimulus intensity is depicted as a color scaling that is independently shown with a scale bar (top left column; for detail, see Takeuchi and Kurahashi, 2008). (B–G) Waveforms of the current induced by the local laser irradiation. Cell was loaded with 10 mM of caged Ca. All ROIs were circular, and diameters were 1 µm (25 pixels) for filled squares or 0.52 µm (13 pixels) for filled circles. Vh, −50 mV. 100× lens. Laser wavelength, 351 and 364 nm. Output, 70%; transmission, 100%. Data were obtained from points indicated in A. Downward transients observed immediately before the responses are artifacts caused by the trigger signals to initiate the raster scan on LSM. (H) Relation between the distance from the knob and local current responses from eight cells. 100× lens. The lowest horizontal color bars indicate the length of the cilia of corresponding colored plots.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2713142&req=5

fig10: Spatial distribution of [Ca]i sensitivity along the single cilium. (A) Fluorescent image of a single cilium and the locations of the UV laser stimuli. Stimulus intensity is depicted as a color scaling that is independently shown with a scale bar (top left column; for detail, see Takeuchi and Kurahashi, 2008). (B–G) Waveforms of the current induced by the local laser irradiation. Cell was loaded with 10 mM of caged Ca. All ROIs were circular, and diameters were 1 µm (25 pixels) for filled squares or 0.52 µm (13 pixels) for filled circles. Vh, −50 mV. 100× lens. Laser wavelength, 351 and 364 nm. Output, 70%; transmission, 100%. Data were obtained from points indicated in A. Downward transients observed immediately before the responses are artifacts caused by the trigger signals to initiate the raster scan on LSM. (H) Relation between the distance from the knob and local current responses from eight cells. 100× lens. The lowest horizontal color bars indicate the length of the cilia of corresponding colored plots.
Mentions: In the experiments of Fig. 10 (local photolysis), a laser-scanning confocal microscope (LSM510; Carl Zeiss, Inc.) equipped with an acousto-optic tunable filter for the laser control was used with a Fluar (DIC) 100×/1.45 NA (oil-immersion) objective lens. The UV laser beam (80 mW: argon laser λ = 351, 364 nm; Coherent) of Zeiss LSM equipped with the region of interest (ROI) function was applied locally to the cilium for photolysis. Argon laser λ = 458 nm was used for visualizing the fluorescence emitted from Lucifer yellow incorporated into the cell via a WC patch pipette, and λ = 488 nm was used for detecting the timing of laser stimulus. The 458- or 488-nm laser beam alone did not cause photolysis when examined with cells. The timing of the light pulse is shown above the current traces in the figures as a downward deflection of the trace.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Frontier Biosciences, Osaka University, Osaka 560-8531, Japan.

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.

Show MeSH
Related in: MedlinePlus