Molecular and functional differences in voltage-activated sodium currents between GABA projection neurons and dopamine neurons in the substantia nigra

Shengyuan Ding, Wei Wei, Fuming Zhou

Research output: Contribution to journalArticle

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Abstract

GABA projection neurons (GABA neurons) in the substantia nigra pars reticulata (SNr) and dopamine projection neurons (DA neurons) in substantia nigra pars compacta (SNc) have strikingly different firing properties. SNc DA neurons fire low-frequency, long-duration spikes, whereas SNr GABA neurons fire high-frequency, short-duration spikes. Since voltage-activated sodium (Na V ) channels are critical to spike generation, the different firing properties raise the possibility that, compared with DA neurons, Na V channels in SNr GABA neurons have higher density, faster kinetics, and less cumulative inactivation. Our quantitative RT-PCR analysis on immunohistochemically identified nigral neurons indicated that mRNAs for poreforming Na V 1.1 and Na V 1.6 subunits and regulatory Na V β1 and Na v β4 subunits are more abundant in SNr GABA neurons than SNc DA neurons. These α-subunits and β-subunits are key subunits for forming Na V channels conducting the transient Na V current (I NaT ), persistent Na current (I NaP ), and resurgent Na current (I NaR ). Nucleated patch-clamp recordings showed that I NaT had a higher density, a steeper voltage-dependent activation, and a faster deactivation in SNr GABA neurons than in SNc DA neurons. I NaT also recovered more quickly from inactivation and had less cumulative inactivation in SNr GABA neurons than in SNc DA neurons. Furthermore, compared with nigral DA neurons, SNr GABA neurons had a larger I NaR and I NaP . Blockade of I NaP induced a larger hyperpolarization in SNr GABA neurons than in SNc DA neurons. Taken together, these results indicate that NaV channels expressed in fast-spiking SNr GABA neurons and slow-spiking SNc DA neurons are tailored to support their different spiking capabilities.

Original languageEnglish (US)
Pages (from-to)3019-3034
Number of pages16
JournalJournal of Neurophysiology
Volume106
Issue number6
DOIs
StatePublished - Dec 1 2011

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GABAergic Neurons
Dopaminergic Neurons
Substantia Nigra
Sodium
Pars Reticulata
Pars Compacta
Neurons
Polymerase Chain Reaction
Messenger RNA

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Physiology

Cite this

Molecular and functional differences in voltage-activated sodium currents between GABA projection neurons and dopamine neurons in the substantia nigra. / Ding, Shengyuan; Wei, Wei; Zhou, Fuming.

In: Journal of Neurophysiology, Vol. 106, No. 6, 01.12.2011, p. 3019-3034.

Research output: Contribution to journalArticle

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AB - GABA projection neurons (GABA neurons) in the substantia nigra pars reticulata (SNr) and dopamine projection neurons (DA neurons) in substantia nigra pars compacta (SNc) have strikingly different firing properties. SNc DA neurons fire low-frequency, long-duration spikes, whereas SNr GABA neurons fire high-frequency, short-duration spikes. Since voltage-activated sodium (Na V ) channels are critical to spike generation, the different firing properties raise the possibility that, compared with DA neurons, Na V channels in SNr GABA neurons have higher density, faster kinetics, and less cumulative inactivation. Our quantitative RT-PCR analysis on immunohistochemically identified nigral neurons indicated that mRNAs for poreforming Na V 1.1 and Na V 1.6 subunits and regulatory Na V β1 and Na v β4 subunits are more abundant in SNr GABA neurons than SNc DA neurons. These α-subunits and β-subunits are key subunits for forming Na V channels conducting the transient Na V current (I NaT ), persistent Na current (I NaP ), and resurgent Na current (I NaR ). Nucleated patch-clamp recordings showed that I NaT had a higher density, a steeper voltage-dependent activation, and a faster deactivation in SNr GABA neurons than in SNc DA neurons. I NaT also recovered more quickly from inactivation and had less cumulative inactivation in SNr GABA neurons than in SNc DA neurons. Furthermore, compared with nigral DA neurons, SNr GABA neurons had a larger I NaR and I NaP . Blockade of I NaP induced a larger hyperpolarization in SNr GABA neurons than in SNc DA neurons. Taken together, these results indicate that NaV channels expressed in fast-spiking SNr GABA neurons and slow-spiking SNc DA neurons are tailored to support their different spiking capabilities.

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