Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT(3A))

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Abstract

1. A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT(3A)) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 2. 5-HT evoked transient inward currents (EC50 = 3.4 μM; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pM) and by the non-selective agents metoclopramide (IC50 = 69 nM), cocaine (IC50 = 459 nM) and (+)-tubocurarine (IC50 = 2.8 μM). 3. 5-HT-induced currents rectified inwardly and reversed in sign (E(5-HT)) at a potential of -2.2 mV. N-Methyl-D-glucamine was finitely permeant. Permeability ratios P(Na)/P(Cs) and P(NMDG)/P(Cs) were 0.90 and 0.083, respectively. 4. Permeability towards divalent cations was assessed from measurements of E(5-HT) in media where Ca2+ and Mg2+ replaced Na+. P(Ca)/P(Cs) and P(Mg)/P(Cs) were calculated to be 1.00 and 0.61, respectively. 5. Single channel chord conductance (γ) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at -40 mV to 742 fS at -100 mV. 6. Reducing [Ca2+](o) from 2 to 0.1 mM caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+](o) produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of γ contributes to this phenomenon. 7. The data indicate that homo-oligomeric receptors composed of h5-HT(3A) subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+.

Original languageEnglish
Pages (from-to)653-665
Number of pages13
JournalJournal of Physiology
Volume507
Issue number3
DOIs
Publication statusPublished - Mar 1998

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Receptors, Serotonin, 5-HT3
Serotonin
Inhibitory Concentration 50
Ions
Patch-Clamp Techniques
Permeability
Serotonin 5-HT3 Receptor Antagonists
Ondansetron
Tubocurarine
Metoclopramide
HEK293 Cells
Divalent Cations
Ion Channels
Cocaine
Cations
Membranes

Cite this

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title = "Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT(3A))",
abstract = "1. A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT(3A)) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 2. 5-HT evoked transient inward currents (EC50 = 3.4 μM; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pM) and by the non-selective agents metoclopramide (IC50 = 69 nM), cocaine (IC50 = 459 nM) and (+)-tubocurarine (IC50 = 2.8 μM). 3. 5-HT-induced currents rectified inwardly and reversed in sign (E(5-HT)) at a potential of -2.2 mV. N-Methyl-D-glucamine was finitely permeant. Permeability ratios P(Na)/P(Cs) and P(NMDG)/P(Cs) were 0.90 and 0.083, respectively. 4. Permeability towards divalent cations was assessed from measurements of E(5-HT) in media where Ca2+ and Mg2+ replaced Na+. P(Ca)/P(Cs) and P(Mg)/P(Cs) were calculated to be 1.00 and 0.61, respectively. 5. Single channel chord conductance (γ) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at -40 mV to 742 fS at -100 mV. 6. Reducing [Ca2+](o) from 2 to 0.1 mM caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+](o) produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of γ contributes to this phenomenon. 7. The data indicate that homo-oligomeric receptors composed of h5-HT(3A) subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+.",
author = "Brown, {A. M.} and Hope, {A. G.} and Lambert, {J. J.} and Peters, {J. A.}",
year = "1998",
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language = "English",
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pages = "653--665",
journal = "Journal of Physiology",
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Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT(3A)). / Brown, A. M.; Hope, A. G.; Lambert, J. J.; Peters, J. A.

In: Journal of Physiology, Vol. 507, No. 3, 03.1998, p. 653-665.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Ion permeation and conduction in a human recombinant 5-HT3 receptor subunit (h5-HT(3A))

AU - Brown, A. M.

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N2 - 1. A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT(3A)) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 2. 5-HT evoked transient inward currents (EC50 = 3.4 μM; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pM) and by the non-selective agents metoclopramide (IC50 = 69 nM), cocaine (IC50 = 459 nM) and (+)-tubocurarine (IC50 = 2.8 μM). 3. 5-HT-induced currents rectified inwardly and reversed in sign (E(5-HT)) at a potential of -2.2 mV. N-Methyl-D-glucamine was finitely permeant. Permeability ratios P(Na)/P(Cs) and P(NMDG)/P(Cs) were 0.90 and 0.083, respectively. 4. Permeability towards divalent cations was assessed from measurements of E(5-HT) in media where Ca2+ and Mg2+ replaced Na+. P(Ca)/P(Cs) and P(Mg)/P(Cs) were calculated to be 1.00 and 0.61, respectively. 5. Single channel chord conductance (γ) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at -40 mV to 742 fS at -100 mV. 6. Reducing [Ca2+](o) from 2 to 0.1 mM caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+](o) produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of γ contributes to this phenomenon. 7. The data indicate that homo-oligomeric receptors composed of h5-HT(3A) subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+.

AB - 1. A human recombinant homo-oligomeric 5-HT3 receptor (h5-HT(3A)) expressed in a human embryonic kidney cell line (HEK 293) was characterized using the whole-cell recording configuration of the patch clamp technique. 2. 5-HT evoked transient inward currents (EC50 = 3.4 μM; Hill coefficient = 1.8) that were blocked by the 5-HT3 receptor antagonist ondansetron (IC50 = 103 pM) and by the non-selective agents metoclopramide (IC50 = 69 nM), cocaine (IC50 = 459 nM) and (+)-tubocurarine (IC50 = 2.8 μM). 3. 5-HT-induced currents rectified inwardly and reversed in sign (E(5-HT)) at a potential of -2.2 mV. N-Methyl-D-glucamine was finitely permeant. Permeability ratios P(Na)/P(Cs) and P(NMDG)/P(Cs) were 0.90 and 0.083, respectively. 4. Permeability towards divalent cations was assessed from measurements of E(5-HT) in media where Ca2+ and Mg2+ replaced Na+. P(Ca)/P(Cs) and P(Mg)/P(Cs) were calculated to be 1.00 and 0.61, respectively. 5. Single channel chord conductance (γ) estimated from fluctuation analysis of macroscopic currents increased with membrane hyperpolarization from 243 fS at -40 mV to 742 fS at -100 mV. 6. Reducing [Ca2+](o) from 2 to 0.1 mM caused an increase in the whole-cell current evoked by 5-HT. A concomitant reduction in [Mg2+](o) produced further potentiation. Fluctuation analysis indicates that a voltage-independent augmentation of γ contributes to this phenomenon. 7. The data indicate that homo-oligomeric receptors composed of h5-HT(3A) subunits form inwardly rectifying cation-selective ion channels of low conductance that are permeable to Ca2+ and Mg2+.

U2 - 10.1111/j.1469-7793.1998.653bs.x

DO - 10.1111/j.1469-7793.1998.653bs.x

M3 - Article

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SP - 653

EP - 665

JO - Journal of Physiology

JF - Journal of Physiology

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