Tetrodotoxin-Sensitive Sodium Channels Mediate Action Potential Firing and Excitability in Menthol-Sensitive Vglut3-Lineage Sensory Neurons

Sensory neurons with afferent axons from the kidney are extraordinary in their response to electrical stimulation. More than 50% exhibit a tonic firing pattern, i.e., sustained action potential firing throughout depolarizing, pointing to an increased excitability, whereas nonrenal neurons show mainly a phasic response, i.e., less than five action potentials. Here we investigated whether these peculiar firing characteristics of renal afferent neurons are due to differences in the expression of voltage-gated sodium channels (Navs). Dorsal root ganglion (DRG) neurons from rats (Th11-L2) were recorded by the current-clamp technique and distinguished as “tonic” or “phasic.” In voltage-clamp recordings, Navs were characterized by their tetrodotoxoxin (TTX) sensitivity, and their molecular identity was revealed by RT-PCR. The firing pattern of 66 DRG neurons (41 renal and 25 nonrenal) was investigated. Renal neurons exhibited more often a tonic firing pattern (56.1 vs. 12%). Tonic neurons showed a more positive threshold (−21.75 ± 1.43 vs.−29.33 ± 1.63 mV; P < 0.05), a higher overshoot (56.74 [53.6–60.96] vs. 46.79 mV [38.63–54.75]; P < 0.05) and longer action potential duration (4.61 [4.15–5.85] vs. 3.35 ms [2.12–5.67]; P < 0.05). These findings point to an increased presence of the TTX-resistant Navs 1.8 and 1.9. Furthermore, tonic neurons exhibited a relatively higher portion of TTX-resistant sodium currents. Interestingly, mRNA expression of TTX-resistant sodium channels was significantly increased in renal, predominantly tonic, DRG neurons. Hence, under physiological conditions, renal sensory neurons exhibit predominantly a firing pattern associated with higher excitability. Our findings support that this is due to an increased expression and activation of TTX-resistant Navs.

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Tetrodotoxin-sensitive sodium channels mediate action potential firing and excitability in menthol-sensitive Vglut3-lineage sensory neurons

10.1101/670620 ◽

2019 ◽

Author(s):

Theanne N. Griffith ◽

Trevor A. Docter ◽

Ellen A. Lumpkin

Keyword(s):

Action Potential ◽

Sodium Channels ◽

Sensory Neurons ◽

Transient Receptor Potential ◽

Small Diameter ◽

Slow Inactivation ◽

Drg Neurons ◽

Action Potential Firing ◽

Transient Receptor Potential Melastatin ◽

Potential Firing

AbstractSmall-diameter vesicular glutamate transporter 3-lineage (Vglut3lineage) dorsal root ganglion (DRG) neurons play an important role in mechanosensation and thermal hypersensitivity; however, little is known about their intrinsic electrical properties. We therefore set out to investigate mechanisms of excitability within this population. Calcium microfluorimetry analysis of male and female mouse DRG neurons demonstrated that the cooling compound menthol selectively activates a subset of Vglut3lineage neurons. Whole-cell recordings showed that small-diameter Vglut3lineage DRG neurons fire menthol-evoked action potentials and exhibited robust, transient receptor potential melastatin 8 (TRPM8)-dependent discharges at room temperature. This heightened excitability was confirmed by current-clamp and action potential phase-plot analyses, which showed menthol-sensitive Vglut3lineage neurons to have more depolarized membrane potentials, lower firing thresholds, and higher evoked firing frequencies compared with menthol-insensitive Vglut3lineage neurons. A biophysical analysis revealed voltage-gated sodium channel (NaV) currents in menthol-sensitive Vglut3lineage neurons were resistant to entry into slow inactivation compared with menthol-insensitive neurons. Multiplex in situ hybridization showed similar distributions of tetrodotoxin (TTX)-sensitive NaVs transcripts between TRPM8-positive and -negative Vglut3lineage neurons; however, NaV1.8 transcripts, which encode TTX-resistant channels, were more prevalent in TRPM8-negative neurons. Conversely, pharmacological analyses identified distinct functional contributions of NaV subunits, with NaV1.1 driving firing in menthol-sensitive neurons, whereas other small-diameter Vglut3lineage neurons rely primarily on TTX-resistant NaV channels. Additionally, when NaV1.1 channels were blocked, the remaining NaV currents readily entered into slow inactivation in menthol-sensitive Vglut3lineage neurons. Thus, these data demonstrate that TTX-sensitive NaVs drive action potential firing in menthol-sensitive sensory neurons and contribute to their heightened excitability.Significance StatementSomatosensensory neurons encode various sensory modalities including thermoreception, mechanoreception, nociception and itch. This report identifies a previously unknown requirement for tetrodotoxin-sensitive sodium channels in action potential firing in a discrete subpopulation of small-diameter sensory neurons that are activated by the cooling agent menthol. Together, our results provide a mechanistic understanding of factors that control intrinsic excitability in functionally distinct subsets of peripheral neurons. Furthermore, as menthol has been used for centuries as an analgesic and anti-pruritic, these findings support the viability of NaV1.1 as a therapeutic target for sensory disorders.

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pigkMutation underliesmachobehavior and affects Rohon-Beard cell excitability

Journal of Neurophysiology ◽

10.1152/jn.00355.2015 ◽

2015 ◽

Vol 114 (2) ◽

pp. 1146-1157 ◽

Cited By ~ 2

Author(s):

V. Carmean ◽

M. A. Yonkers ◽

M. B. Tellez ◽

J. R. Willer ◽

G. B. Willer ◽

...

Keyword(s):

Action Potential ◽

Sensory Neurons ◽

Sodium Current ◽

Genetic Defect ◽

Sensory Cells ◽

Loss Of Function ◽

Wild Type ◽

Action Potential Firing ◽

Potential Firing ◽

Touch Response

The study of touch-evoked behavior allows investigation of both the cells and circuits that generate a response to tactile stimulation. We investigate a touch-insensitive zebrafish mutant, macho (maco), previously shown to have reduced sodium current amplitude and lack of action potential firing in sensory neurons. In the genomes of mutant but not wild-type embryos, we identify a mutation in the pigk gene. The encoded protein, PigK, functions in attachment of glycophosphatidylinositol anchors to precursor proteins. In wild-type embryos, pigk mRNA is present at times when mutant embryos display behavioral phenotypes. Consistent with the predicted loss of function induced by the mutation, knock-down of PigK phenocopies maco touch insensitivity and leads to reduced sodium current (INa) amplitudes in sensory neurons. We further test whether the genetic defect in pigk underlies the maco phenotype by overexpressing wild-type pigk in mutant embryos. We find that ubiquitous expression of wild-type pigk rescues the touch response in maco mutants. In addition, for maco mutants, expression of wild-type pigk restricted to sensory neurons rescues sodium current amplitudes and action potential firing in sensory neurons. However, expression of wild-type pigk limited to sensory cells of mutant embryos does not allow rescue of the behavioral touch response. Our results demonstrate an essential role for pigk in generation of the touch response beyond that required for maintenance of proper INa density and action potential firing in sensory neurons.

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Activation of Kainate Receptors on Rat Sensory Neurons Evokes Action Potential Firing and May Modulate Transmitter Release

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1999.tb11325.x ◽

1999 ◽

Vol 868 (1 MOLECULAR AND) ◽

pp. 546-549 ◽

Cited By ~ 11

Author(s):

C. JUSTIN LEE ◽

H. S. ENGELMAN ◽

A. B. MacCDERMOTT

Keyword(s):

Action Potential ◽

Sensory Neurons ◽

Transmitter Release ◽

Kainate Receptors ◽

Action Potential Firing ◽

Potential Firing

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TMEM16A and TMEM16B modulate pheromone-evoked action potential firing in mouse vomeronasal sensory neurons

eNeuro ◽

10.1523/eneuro.0179-21.2021 ◽

2021 ◽

pp. ENEURO.0179-21.2021

Author(s):

Andres Hernandez-Clavijo ◽

Nicole Sarno ◽

Kevin Y. Gonzalez-Velandia ◽

Rudolf Degen ◽

David Fleck ◽

...

Keyword(s):

Action Potential ◽

Sensory Neurons ◽

Action Potential Firing ◽

Potential Firing ◽

Vomeronasal Sensory Neurons

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Carisbamate, a novel neuromodulator, inhibits voltage-gated sodium channels and action potential firing of rat hippocampal neurons

Epilepsy Research ◽

10.1016/j.eplepsyres.2008.09.006 ◽

2009 ◽

Vol 83 (1) ◽

pp. 66-72 ◽

Cited By ~ 23

Author(s):

Yi Liu ◽

George J. Yohrling ◽

Yan Wang ◽

Tasha L. Hutchinson ◽

Douglas E. Brenneman ◽

...

Keyword(s):

Action Potential ◽

Sodium Channels ◽

Hippocampal Neurons ◽

Action Potential Firing ◽

Voltage Gated ◽

Voltage Gated Sodium Channels ◽

Potential Firing

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Spike-frequency dependent inhibition and excitation of neural activity by high-frequency ultrasound

10.1101/2020.06.01.128710 ◽

2020 ◽

Author(s):

Martin Loynaz Prieto ◽

Kamyar Firouzi ◽

Butrus T. Khuri-Yakub ◽

Daniel V. Madison ◽

Merritt Maduke

Keyword(s):

Action Potential ◽

Sodium Channels ◽

High Frequency ◽

Pyramidal Neurons ◽

Potassium Conductance ◽

Firing Frequency ◽

Resting Membrane Potential ◽

Action Potential Firing ◽

Voltage Dependent ◽

Potential Firing

ABSTRACTUltrasound can modulate action-potential firing in vivo and in vitro, but the mechanistic basis of this phenomenon is not well understood. To address this problem, we used patch-clamp recording to quantify the effects of focused, high-frequency (43 MHz) ultrasound on evoked action potential firing in CA1 pyramidal neurons in acute rodent hippocampal brain slices. We find that ultrasound can either inhibit or potentiate firing in a spike-frequency-dependent manner: at low (near-threshold) input currents and low firing frequencies, ultrasound inhibits firing, while at higher input currents and higher firing frequencies, ultrasound potentiates firing. The net result of these two competing effects is that ultrasound increases the threshold current for action potential firing, the slope of frequency-input curves, and the maximum firing frequency. In addition, ultrasound slightly hyperpolarizes the resting membrane potential, decreases action potential width, and increases the depth of the afterhyperpolarization. All of these results can be explained by the hypothesis that ultrasound activates a sustained potassium conductance. According to this hypothesis, increased outward potassium currents hyperpolarize the resting membrane potential and inhibit firing at near-threshold input currents, but potentiate firing in response to higher input currents by limiting inactivation of voltage-dependent sodium channels during the action potential. This latter effect is a consequence of faster action-potential repolarization, which limits inactivation of voltage-dependent sodium channels, and deeper (more negative) afterhyperpolarization, which increases the rate of recovery from inactivation. Based on these results we propose that ultrasound activates thermosensitive and mechanosensitive two-pore-domain potassium (K2P) channels, through heating or mechanical effects of acoustic radiation force. Finite-element modelling of the effects of ultrasound on brain tissue suggests that the effects of ultrasound on firing frequency are caused by a small (less than 2°C) increase in temperature, with possible additional contributions from mechanical effectsSUMMARYPrieto et al. describe how ultrasound can either inhibit or potentiate action potential firing in hippocampal pyramidal neurons and demonstrate that these effects can be explained by increased potassium conductance.

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Spike frequency–dependent inhibition and excitation of neural activity by high-frequency ultrasound

The Journal of General Physiology ◽

10.1085/jgp.202012672 ◽

2020 ◽

Vol 152 (11) ◽

Author(s):

Martin Loynaz Prieto ◽

Kamyar Firouzi ◽

Butrus T. Khuri-Yakub ◽

Daniel V. Madison ◽

Merritt Maduke

Keyword(s):

Membrane Potential ◽

Action Potential ◽

Sodium Channels ◽

High Frequency ◽

Firing Frequency ◽

Resting Membrane Potential ◽

Action Potential Firing ◽

Mechanical Effects ◽

Voltage Dependent ◽

Potential Firing

Ultrasound can modulate action potential firing in vivo and in vitro, but the mechanistic basis of this phenomenon is not well understood. To address this problem, we used patch-clamp recording to quantify the effects of focused, high-frequency (43 MHz) ultrasound on evoked action potential firing in CA1 pyramidal neurons in acute rodent hippocampal brain slices. We find that ultrasound can either inhibit or potentiate firing in a spike frequency–dependent manner: at low (near-threshold) input currents and low firing frequencies, ultrasound inhibits firing, while at higher input currents and higher firing frequencies, ultrasound potentiates firing. The net result of these two competing effects is that ultrasound increases the threshold current for action potential firing, the slope of frequency-input curves, and the maximum firing frequency. In addition, ultrasound slightly hyperpolarizes the resting membrane potential, decreases action potential width, and increases the depth of the after-hyperpolarization. All of these results can be explained by the hypothesis that ultrasound activates a sustained potassium conductance. According to this hypothesis, increased outward potassium currents hyperpolarize the resting membrane potential and inhibit firing at near-threshold input currents but potentiate firing in response to higher-input currents by limiting inactivation of voltage-dependent sodium channels during the action potential. This latter effect is a consequence of faster action potential repolarization, which limits inactivation of voltage-dependent sodium channels, and deeper (more negative) after-hyperpolarization, which increases the rate of recovery from inactivation. Based on these results, we propose that ultrasound activates thermosensitive and mechanosensitive two-pore-domain potassium (K2P) channels through heating or mechanical effects of acoustic radiation force. Finite-element modeling of the effects of ultrasound on brain tissue suggests that the effects of ultrasound on firing frequency are caused by a small (<2°C) increase in temperature, with possible additional contributions from mechanical effects.

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