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Responses of Xenopus laevis water nose to water-soluble and volatile odorants.

Iida A, Kashiwayanagi M - J. Gen. Physiol. (1999)

Bottom Line: Under voltage-clamp conditions, a voltage-dependent Na+ inward current, a sustained outward K+ current, and a Ca2+-activated K+ current were identified.The application of alanine or arginine induced inward currents in a dose-dependent manner.More than 50% of the single olfactory neurons responded to multiple types of amino acids, including acidic, neutral, and basic amino acids applied at 100 microM or 1 mM.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, Japan.

ABSTRACT
Using the whole-cell mode of the patch-clamp technique, we recorded action potentials, voltage-activated cationic currents, and inward currents in response to water-soluble and volatile odorants from receptor neurons in the lateral diverticulum (water nose) of the olfactory sensory epithelium of Xenopus laevis. The resting membrane potential was -46.5 +/- 1.2 mV (mean +/- SEM, n = 68), and a current injection of 1-3 pA induced overshooting action potentials. Under voltage-clamp conditions, a voltage-dependent Na+ inward current, a sustained outward K+ current, and a Ca2+-activated K+ current were identified. Application of an amino acid cocktail induced inward currents in 32 of 238 olfactory neurons in the lateral diverticulum under voltage-clamp conditions. Application of volatile odorant cocktails also induced current responses in 23 of 238 olfactory neurons. These results suggest that the olfactory neurons respond to both water-soluble and volatile odorants. The application of alanine or arginine induced inward currents in a dose-dependent manner. More than 50% of the single olfactory neurons responded to multiple types of amino acids, including acidic, neutral, and basic amino acids applied at 100 microM or 1 mM. These results suggest that olfactory neurons in the lateral diverticulum have receptors for amino acids and volatile odorants.

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(A) The currents seen under voltage-clamp conditions in response to negative and positive voltage pulses from –70 mV. (B) Current–voltage relations. The peak of the transient inward current (•) and the outward current (○). Isolated Na+ currents from olfactory neurons in the lateral diverticulum. The voltage-activated Na+ current is blocked after the substitution of Na+ with choline in the external solution (C) or the addition of 1 μM TTX to the external solution (D). The internal solution contained (mM): 115 CsCl, 2 MgCl2, 2 EGTA, 10 HEPES-NaOH, pH 7.4. The external EGTA solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-NaOH, pH 7.4. Isolated K+ currents in olfactory receptor neurons in the lateral diverticulum of Xenopus laevis, and the effect of the application of TEA and the elimination of Ca2+ (E–H). (E) The K+ current responses to positive voltage pulses from a holding potential of −70 mV. This current was reversibly blocked by 25 mM TEA (F and G). The external solution contained (mM): 116 N-methyl-d-glucamine, 1 EGTA, 2 CoCl2, 10 glucose, 10 HEPES-KOH, pH 7.4. (H) The outward K+ current is partially attenuated by the elimination of Ca2+ from the external solution. The Ca2+-free solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-KOH, pH 7.4.
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Figure 3: (A) The currents seen under voltage-clamp conditions in response to negative and positive voltage pulses from –70 mV. (B) Current–voltage relations. The peak of the transient inward current (•) and the outward current (○). Isolated Na+ currents from olfactory neurons in the lateral diverticulum. The voltage-activated Na+ current is blocked after the substitution of Na+ with choline in the external solution (C) or the addition of 1 μM TTX to the external solution (D). The internal solution contained (mM): 115 CsCl, 2 MgCl2, 2 EGTA, 10 HEPES-NaOH, pH 7.4. The external EGTA solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-NaOH, pH 7.4. Isolated K+ currents in olfactory receptor neurons in the lateral diverticulum of Xenopus laevis, and the effect of the application of TEA and the elimination of Ca2+ (E–H). (E) The K+ current responses to positive voltage pulses from a holding potential of −70 mV. This current was reversibly blocked by 25 mM TEA (F and G). The external solution contained (mM): 116 N-methyl-d-glucamine, 1 EGTA, 2 CoCl2, 10 glucose, 10 HEPES-KOH, pH 7.4. (H) The outward K+ current is partially attenuated by the elimination of Ca2+ from the external solution. The Ca2+-free solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-KOH, pH 7.4.

Mentions: Voltage-clamp recordings confirm that the current responsible for the rising phase of the current-induced action potential is carried by Na+. Fig. 3 A shows the two major currents elicited by the depolarizing steps of voltage from a holding potential of −70 mV. A transient inward current appeared at greater than −40 mV, and an outward current was observed after the rapid inward current. The current–voltage curves taken at the peak of the inward and outward currents are shown in Fig. 3 B.


Responses of Xenopus laevis water nose to water-soluble and volatile odorants.

Iida A, Kashiwayanagi M - J. Gen. Physiol. (1999)

(A) The currents seen under voltage-clamp conditions in response to negative and positive voltage pulses from –70 mV. (B) Current–voltage relations. The peak of the transient inward current (•) and the outward current (○). Isolated Na+ currents from olfactory neurons in the lateral diverticulum. The voltage-activated Na+ current is blocked after the substitution of Na+ with choline in the external solution (C) or the addition of 1 μM TTX to the external solution (D). The internal solution contained (mM): 115 CsCl, 2 MgCl2, 2 EGTA, 10 HEPES-NaOH, pH 7.4. The external EGTA solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-NaOH, pH 7.4. Isolated K+ currents in olfactory receptor neurons in the lateral diverticulum of Xenopus laevis, and the effect of the application of TEA and the elimination of Ca2+ (E–H). (E) The K+ current responses to positive voltage pulses from a holding potential of −70 mV. This current was reversibly blocked by 25 mM TEA (F and G). The external solution contained (mM): 116 N-methyl-d-glucamine, 1 EGTA, 2 CoCl2, 10 glucose, 10 HEPES-KOH, pH 7.4. (H) The outward K+ current is partially attenuated by the elimination of Ca2+ from the external solution. The Ca2+-free solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-KOH, pH 7.4.
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Related In: Results  -  Collection

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Figure 3: (A) The currents seen under voltage-clamp conditions in response to negative and positive voltage pulses from –70 mV. (B) Current–voltage relations. The peak of the transient inward current (•) and the outward current (○). Isolated Na+ currents from olfactory neurons in the lateral diverticulum. The voltage-activated Na+ current is blocked after the substitution of Na+ with choline in the external solution (C) or the addition of 1 μM TTX to the external solution (D). The internal solution contained (mM): 115 CsCl, 2 MgCl2, 2 EGTA, 10 HEPES-NaOH, pH 7.4. The external EGTA solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-NaOH, pH 7.4. Isolated K+ currents in olfactory receptor neurons in the lateral diverticulum of Xenopus laevis, and the effect of the application of TEA and the elimination of Ca2+ (E–H). (E) The K+ current responses to positive voltage pulses from a holding potential of −70 mV. This current was reversibly blocked by 25 mM TEA (F and G). The external solution contained (mM): 116 N-methyl-d-glucamine, 1 EGTA, 2 CoCl2, 10 glucose, 10 HEPES-KOH, pH 7.4. (H) The outward K+ current is partially attenuated by the elimination of Ca2+ from the external solution. The Ca2+-free solution contained (mM): 116 NaCl, 4 KCl, 1 MgCl2, 1 EGTA, 10 glucose, 10 HEPES-KOH, pH 7.4.
Mentions: Voltage-clamp recordings confirm that the current responsible for the rising phase of the current-induced action potential is carried by Na+. Fig. 3 A shows the two major currents elicited by the depolarizing steps of voltage from a holding potential of −70 mV. A transient inward current appeared at greater than −40 mV, and an outward current was observed after the rapid inward current. The current–voltage curves taken at the peak of the inward and outward currents are shown in Fig. 3 B.

Bottom Line: Under voltage-clamp conditions, a voltage-dependent Na+ inward current, a sustained outward K+ current, and a Ca2+-activated K+ current were identified.The application of alanine or arginine induced inward currents in a dose-dependent manner.More than 50% of the single olfactory neurons responded to multiple types of amino acids, including acidic, neutral, and basic amino acids applied at 100 microM or 1 mM.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, Japan.

ABSTRACT
Using the whole-cell mode of the patch-clamp technique, we recorded action potentials, voltage-activated cationic currents, and inward currents in response to water-soluble and volatile odorants from receptor neurons in the lateral diverticulum (water nose) of the olfactory sensory epithelium of Xenopus laevis. The resting membrane potential was -46.5 +/- 1.2 mV (mean +/- SEM, n = 68), and a current injection of 1-3 pA induced overshooting action potentials. Under voltage-clamp conditions, a voltage-dependent Na+ inward current, a sustained outward K+ current, and a Ca2+-activated K+ current were identified. Application of an amino acid cocktail induced inward currents in 32 of 238 olfactory neurons in the lateral diverticulum under voltage-clamp conditions. Application of volatile odorant cocktails also induced current responses in 23 of 238 olfactory neurons. These results suggest that the olfactory neurons respond to both water-soluble and volatile odorants. The application of alanine or arginine induced inward currents in a dose-dependent manner. More than 50% of the single olfactory neurons responded to multiple types of amino acids, including acidic, neutral, and basic amino acids applied at 100 microM or 1 mM. These results suggest that olfactory neurons in the lateral diverticulum have receptors for amino acids and volatile odorants.

Show MeSH
Related in: MedlinePlus