Sodium current in rat and cat thalamocortical neurons: role of a non-inactivating component in tonic and burst firing

H. Rheinallt Parri, Vincenzo Crunelli

Research output: Contribution to journalArticle

Abstract

The properties of the Na+ current present in thalamocortical neurons of the dorsal lateral geniculate nucleus were investigated in dissociated neonate rat and cat neurons and in neurons from slices of neonate and adult rats using patch and sharp electrode recordings. The steady-state activation and inactivation of the transient Na+ current (INa) was well fitted with a Boltzmann curve (voltage of half-maximal activation and inactivation, V1/2, -29.84 mV and -70.04 mV, respectively).

Steady-state activation and inactivation curves showed a small region of overlap, indicating the occurrence of a / Na window current.  / Na decay could be fitted with a single exponential function, consistent with the presence of only one channel type.

Voltage ramp and step protocols showed the presence of a noninactivating component of the Na+ current (/ NaP) that activated at potentials more negative (V1/2 = -56.93 mV) than those of INa. The maximal amplitude of / NaP was approximately 2.5% of INa, thus significantly greater than the calculated contribution (0.2%) of the I Na window component. Comparison of results from dissociated neurons and neurons in slices suggested a dendritic as well as a somatic localization of I NaP. Inclusion of papain in the patch electrode removed the fast inactivation of / Na and induced a current with voltage-dependence (V1/2 = -56.92) and activation parameters similar to those of I NaP.

Current-clamp recordings with sharp electrodes showed that I NaP contributed to depolarizations evoked from potentials of approximately -60 mV and unexpectedly to the amplitude and latency of low-threshold Ca2+ potentials, suggesting that this noninactivating component of the Na+ channel population plays an important role in the integrative properties of thalamocortical neurons during both tonic and burst-firing patterns.
Original languageEnglish
Pages (from-to)854-67
Number of pages14
JournalJournal of Neuroscience
Volume18
Issue number3
DOIs
Publication statusPublished - 1 Feb 1998

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Cats
Sodium
Neurons
Electrodes
Geniculate Bodies
Architectural Accessibility
Papain
Evoked Potentials
Population

Bibliographical note

Articles are released under a Creative Commons Attribution License after a 6 months embargo

Keywords

  • thalamus
  • action potential
  • persistent Na 1 current
  • inactivation
  • burst firing
  • orsal lateral geniculate nucleus

Cite this

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title = "Sodium current in rat and cat thalamocortical neurons: role of a non-inactivating component in tonic and burst firing",
abstract = "The properties of the Na+ current present in thalamocortical neurons of the dorsal lateral geniculate nucleus were investigated in dissociated neonate rat and cat neurons and in neurons from slices of neonate and adult rats using patch and sharp electrode recordings. The steady-state activation and inactivation of the transient Na+ current (INa) was well fitted with a Boltzmann curve (voltage of half-maximal activation and inactivation, V1/2, -29.84 mV and -70.04 mV, respectively). Steady-state activation and inactivation curves showed a small region of overlap, indicating the occurrence of a / Na window current.  / Na decay could be fitted with a single exponential function, consistent with the presence of only one channel type.Voltage ramp and step protocols showed the presence of a noninactivating component of the Na+ current (/ NaP) that activated at potentials more negative (V1/2 = -56.93 mV) than those of INa. The maximal amplitude of / NaP was approximately 2.5{\%} of INa, thus significantly greater than the calculated contribution (0.2{\%}) of the I Na window component. Comparison of results from dissociated neurons and neurons in slices suggested a dendritic as well as a somatic localization of I NaP. Inclusion of papain in the patch electrode removed the fast inactivation of / Na and induced a current with voltage-dependence (V1/2 = -56.92) and activation parameters similar to those of I NaP.Current-clamp recordings with sharp electrodes showed that I NaP contributed to depolarizations evoked from potentials of approximately -60 mV and unexpectedly to the amplitude and latency of low-threshold Ca2+ potentials, suggesting that this noninactivating component of the Na+ channel population plays an important role in the integrative properties of thalamocortical neurons during both tonic and burst-firing patterns.",
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Sodium current in rat and cat thalamocortical neurons : role of a non-inactivating component in tonic and burst firing. / Parri, H. Rheinallt; Crunelli, Vincenzo.

In: Journal of Neuroscience, Vol. 18, No. 3, 01.02.1998, p. 854-67.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Sodium current in rat and cat thalamocortical neurons

T2 - role of a non-inactivating component in tonic and burst firing

AU - Parri, H. Rheinallt

AU - Crunelli, Vincenzo

N1 - Articles are released under a Creative Commons Attribution License after a 6 months embargo

PY - 1998/2/1

Y1 - 1998/2/1

N2 - The properties of the Na+ current present in thalamocortical neurons of the dorsal lateral geniculate nucleus were investigated in dissociated neonate rat and cat neurons and in neurons from slices of neonate and adult rats using patch and sharp electrode recordings. The steady-state activation and inactivation of the transient Na+ current (INa) was well fitted with a Boltzmann curve (voltage of half-maximal activation and inactivation, V1/2, -29.84 mV and -70.04 mV, respectively). Steady-state activation and inactivation curves showed a small region of overlap, indicating the occurrence of a / Na window current.  / Na decay could be fitted with a single exponential function, consistent with the presence of only one channel type.Voltage ramp and step protocols showed the presence of a noninactivating component of the Na+ current (/ NaP) that activated at potentials more negative (V1/2 = -56.93 mV) than those of INa. The maximal amplitude of / NaP was approximately 2.5% of INa, thus significantly greater than the calculated contribution (0.2%) of the I Na window component. Comparison of results from dissociated neurons and neurons in slices suggested a dendritic as well as a somatic localization of I NaP. Inclusion of papain in the patch electrode removed the fast inactivation of / Na and induced a current with voltage-dependence (V1/2 = -56.92) and activation parameters similar to those of I NaP.Current-clamp recordings with sharp electrodes showed that I NaP contributed to depolarizations evoked from potentials of approximately -60 mV and unexpectedly to the amplitude and latency of low-threshold Ca2+ potentials, suggesting that this noninactivating component of the Na+ channel population plays an important role in the integrative properties of thalamocortical neurons during both tonic and burst-firing patterns.

AB - The properties of the Na+ current present in thalamocortical neurons of the dorsal lateral geniculate nucleus were investigated in dissociated neonate rat and cat neurons and in neurons from slices of neonate and adult rats using patch and sharp electrode recordings. The steady-state activation and inactivation of the transient Na+ current (INa) was well fitted with a Boltzmann curve (voltage of half-maximal activation and inactivation, V1/2, -29.84 mV and -70.04 mV, respectively). Steady-state activation and inactivation curves showed a small region of overlap, indicating the occurrence of a / Na window current.  / Na decay could be fitted with a single exponential function, consistent with the presence of only one channel type.Voltage ramp and step protocols showed the presence of a noninactivating component of the Na+ current (/ NaP) that activated at potentials more negative (V1/2 = -56.93 mV) than those of INa. The maximal amplitude of / NaP was approximately 2.5% of INa, thus significantly greater than the calculated contribution (0.2%) of the I Na window component. Comparison of results from dissociated neurons and neurons in slices suggested a dendritic as well as a somatic localization of I NaP. Inclusion of papain in the patch electrode removed the fast inactivation of / Na and induced a current with voltage-dependence (V1/2 = -56.92) and activation parameters similar to those of I NaP.Current-clamp recordings with sharp electrodes showed that I NaP contributed to depolarizations evoked from potentials of approximately -60 mV and unexpectedly to the amplitude and latency of low-threshold Ca2+ potentials, suggesting that this noninactivating component of the Na+ channel population plays an important role in the integrative properties of thalamocortical neurons during both tonic and burst-firing patterns.

KW - thalamus

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KW - persistent Na 1 current

KW - inactivation

KW - burst firing

KW - orsal lateral geniculate nucleus

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U2 - 10.1523/JNEUROSCI.18-03-00854.1998

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