Limits...
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.

Show MeSH

Related in: MedlinePlus

Off-kinetics of the Ca2+-induced current. (A) Effect of cytoplasmic ATP and K+ for Ca2+ extrusion system in the cilia. Relaxation times (τ) were obtained from the exponential fitting of the falling phase in the wave forms at each time (see Fig. 4 D). Vh = −50 mV. Filled black squares, data obtained with 119 mM CsCl pipette solution and 0 mM ATP; filled red squares, data with 119 mM CsCl pipette solution and 1 mM ATP; filled green squares, data with 119 mM KCl and 2 mM ATP. Intensity, 0.48; duration, 200 ms. Plots indicate mean values, and the error bars show SD. Numbers in parentheses indicate the number of examined cells. (B) Voltage dependence of Ca2+ responses. Vh = −50 mV (black) as a control, Vh = +100 mV (red), and Vh = −50 mV (green) as a recovery. (C) Comparison between the falling phases at −50 and +100 mV. Data were obtained from B. Vh = −50 mV (black), Vh = +100 mV (red), and Vh = −50 mV (green). Falling phases were fitted by the single-exponential curve as smooth lines. τ: 91.6 ms (black), 343.3 ms (red), and 160.3 ms (green), respectively. Light intensity was 0.48. (D) Effect of lowered [Na+]o on the Ca2+-induced current in 110 NaCl bath solution (black), 0 mM Na puff application (red), and 110 NaCl bath solution (green). The opening diameter of the puffer was ∼3 µm. 0 mM Na solution was applied 2 s before the light stimulation and continued for 6 s Light stimulation was 0.48. Pressure of puff was 150 kPa. Vh = −50 mV.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig5: Off-kinetics of the Ca2+-induced current. (A) Effect of cytoplasmic ATP and K+ for Ca2+ extrusion system in the cilia. Relaxation times (τ) were obtained from the exponential fitting of the falling phase in the wave forms at each time (see Fig. 4 D). Vh = −50 mV. Filled black squares, data obtained with 119 mM CsCl pipette solution and 0 mM ATP; filled red squares, data with 119 mM CsCl pipette solution and 1 mM ATP; filled green squares, data with 119 mM KCl and 2 mM ATP. Intensity, 0.48; duration, 200 ms. Plots indicate mean values, and the error bars show SD. Numbers in parentheses indicate the number of examined cells. (B) Voltage dependence of Ca2+ responses. Vh = −50 mV (black) as a control, Vh = +100 mV (red), and Vh = −50 mV (green) as a recovery. (C) Comparison between the falling phases at −50 and +100 mV. Data were obtained from B. Vh = −50 mV (black), Vh = +100 mV (red), and Vh = −50 mV (green). Falling phases were fitted by the single-exponential curve as smooth lines. τ: 91.6 ms (black), 343.3 ms (red), and 160.3 ms (green), respectively. Light intensity was 0.48. (D) Effect of lowered [Na+]o on the Ca2+-induced current in 110 NaCl bath solution (black), 0 mM Na puff application (red), and 110 NaCl bath solution (green). The opening diameter of the puffer was ∼3 µm. 0 mM Na solution was applied 2 s before the light stimulation and continued for 6 s Light stimulation was 0.48. Pressure of puff was 150 kPa. Vh = −50 mV.

Mentions: For the experiments of off-kinetics of the Ca2+-induced current (see Fig. 5), K-dominant solution having (in mM) 119 KCl, 1 CaCl2, 5 EGTA, 10 HEPES, and 2 Mg-ATP (pH adjusted to 7.4 with KOH) was used. For 0 Na experiments, solution having (in mM) 110 choline Cl, 3.7 KCl, 3 CaCl2, 1 MgCl2, 10 HEPES, 15 glucose, and 1 pyruvate (pH adjusted to 7.4 with KOH) was used. The pipette resistance was 10–15 MΩ.


Mechanism of olfactory masking in the sensory cilia.

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

Off-kinetics of the Ca2+-induced current. (A) Effect of cytoplasmic ATP and K+ for Ca2+ extrusion system in the cilia. Relaxation times (τ) were obtained from the exponential fitting of the falling phase in the wave forms at each time (see Fig. 4 D). Vh = −50 mV. Filled black squares, data obtained with 119 mM CsCl pipette solution and 0 mM ATP; filled red squares, data with 119 mM CsCl pipette solution and 1 mM ATP; filled green squares, data with 119 mM KCl and 2 mM ATP. Intensity, 0.48; duration, 200 ms. Plots indicate mean values, and the error bars show SD. Numbers in parentheses indicate the number of examined cells. (B) Voltage dependence of Ca2+ responses. Vh = −50 mV (black) as a control, Vh = +100 mV (red), and Vh = −50 mV (green) as a recovery. (C) Comparison between the falling phases at −50 and +100 mV. Data were obtained from B. Vh = −50 mV (black), Vh = +100 mV (red), and Vh = −50 mV (green). Falling phases were fitted by the single-exponential curve as smooth lines. τ: 91.6 ms (black), 343.3 ms (red), and 160.3 ms (green), respectively. Light intensity was 0.48. (D) Effect of lowered [Na+]o on the Ca2+-induced current in 110 NaCl bath solution (black), 0 mM Na puff application (red), and 110 NaCl bath solution (green). The opening diameter of the puffer was ∼3 µm. 0 mM Na solution was applied 2 s before the light stimulation and continued for 6 s Light stimulation was 0.48. Pressure of puff was 150 kPa. Vh = −50 mV.
© Copyright Policy - openaccess
Related In: Results  -  Collection

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

fig5: Off-kinetics of the Ca2+-induced current. (A) Effect of cytoplasmic ATP and K+ for Ca2+ extrusion system in the cilia. Relaxation times (τ) were obtained from the exponential fitting of the falling phase in the wave forms at each time (see Fig. 4 D). Vh = −50 mV. Filled black squares, data obtained with 119 mM CsCl pipette solution and 0 mM ATP; filled red squares, data with 119 mM CsCl pipette solution and 1 mM ATP; filled green squares, data with 119 mM KCl and 2 mM ATP. Intensity, 0.48; duration, 200 ms. Plots indicate mean values, and the error bars show SD. Numbers in parentheses indicate the number of examined cells. (B) Voltage dependence of Ca2+ responses. Vh = −50 mV (black) as a control, Vh = +100 mV (red), and Vh = −50 mV (green) as a recovery. (C) Comparison between the falling phases at −50 and +100 mV. Data were obtained from B. Vh = −50 mV (black), Vh = +100 mV (red), and Vh = −50 mV (green). Falling phases were fitted by the single-exponential curve as smooth lines. τ: 91.6 ms (black), 343.3 ms (red), and 160.3 ms (green), respectively. Light intensity was 0.48. (D) Effect of lowered [Na+]o on the Ca2+-induced current in 110 NaCl bath solution (black), 0 mM Na puff application (red), and 110 NaCl bath solution (green). The opening diameter of the puffer was ∼3 µm. 0 mM Na solution was applied 2 s before the light stimulation and continued for 6 s Light stimulation was 0.48. Pressure of puff was 150 kPa. Vh = −50 mV.
Mentions: For the experiments of off-kinetics of the Ca2+-induced current (see Fig. 5), K-dominant solution having (in mM) 119 KCl, 1 CaCl2, 5 EGTA, 10 HEPES, and 2 Mg-ATP (pH adjusted to 7.4 with KOH) was used. For 0 Na experiments, solution having (in mM) 110 choline Cl, 3.7 KCl, 3 CaCl2, 1 MgCl2, 10 HEPES, 15 glucose, and 1 pyruvate (pH adjusted to 7.4 with KOH) was used. The pipette resistance was 10–15 MΩ.

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