DOI: 10.5061/dryad.k3j9kd5f7
title: Effects of transient, persistent, and resurgent sodium currents on excitability and spike regularity in vestibular ganglion neurons

description: Vestibular afferent neurons occur as two populations with differences in
 spike timing regularity that are independent of rate. The more
 excitable regular afferents have lower current thresholds and
 sustained spiking responses to injected currents, while irregular
 afferent neurons have higher thresholds and transient
 responses. Differences in expression of low-voltage-activated
 potassium (KLV) channels are emphasized in models of spiking
 regularity and excitability in these neurons, leaving open the
 potential contributions of the voltage-gated sodium (NaV)
 channels responsible for the spike upstroke. We investigated the
 impact of different NaV current modes (transient, persistent, and
 resurgent) with whole-cell patch clamp experiments in mouse
 vestibular ganglion neurons (VGNs), the cultured and dissociated
 cell bodies of afferents. All VGNs had transient NaV current,
 many had a small persistent (non-inactivating) NaV current, and a
 few had resurgent current, which flows after the spike when NaV
 channels that were blocked are unblocked. A known NaV1.6 channel
 blocker decreased spike rate and altered spike waveforms in both
 sustained and transient VGNs and affected all three modes of NaV
 current. A NaV channel agonist enhanced persistent current and
 increased spike rate and regularity. We hypothesized that
 persistent and resurgent currents have different effects on
 sustained (regular) VGNs vs. transient (irregular) VGNs. Lacking
 blockers specific for the different current modes, we used modeling
 to isolate their effects on spiking of simulated transient and
 sustained VGNs, driven by simulated current steps and noisy
 trains of simulated EPSCs. In all simulated neurons, increasing
 transient NaV current increased spike rate and
 rate-independent regularity. In simulated sustained VGNs, adding
 persistent current increased both rate and rate-independent
 regularity, while adding resurgent current had limited impact. In
 transient VGNs, adding persistent current had little impact, while
 adding resurgent current increased both rate and rate-independent
 irregularity by enhancing sensitivity to synaptic noise. These
 experiments show that the small NaV current modes may enhance the
 differentiation of afferent populations, with persistent currents
 selectively making regular afferents more regular and resurgent
 currents selectively making irregular afferents more irregular.
description: This dataset includes data from isolated mouse neurons via
 whole-cell patch clamp electrophysiology. We present data of currents
 isolated with pharmacological assays. We also include data from a custom
 single-compartment Hodgkin-Huxley model of neuronal firing. 
description: # Effects of transient, persistent, and resurgent sodium currents on
 excitability and spike regularity in vestibular ganglion neurons
 [https://doi.org/10.5061/dryad.k3j9kd5f7](https://doi.org/10.5061/dryad.k3j9kd5f7) These datasets contain processed data used in the analyses of patch clamp electrophysiology of isolated and cultured vestibular ganglion neurons (VGNs) from mice, and data produced from a single compartment model of neuronal firing. This study investigates how different forms of NaV currents (transient, persistent, and resurgent) alter spiking excitability and regularity in vestibular ganglion neurons.  ## Sharing/Access Information Datasets are in Excel format. Datasets have headers, and additional information is provided in this document. Any blank cells or cells with "n/a" indicate a lack of data for that variable and observation.  ## Description of the data and file structures ### Files overview: For a description of how patch clamping data were collected and modeling data generated, please refer to the Methods section of the manuscript (Baeza-Loya and Eatock, 2024).   Each file corresponds to a figure in the manuscript and contains sufficient data to recreate all plots and statistical tests. Each .xlsx file contains sheets that are explicitly labelled to refer to a panel or subset of data within that figure. Each sheet has unambiguous header information describing the parameter (voltage, current), condition (e.g., drug), and the unique CellID of every cell used in the analysis. Figures 1 through 7 and Supplementary Figures 1 through 3, you can find the exemplars of voltage and current clamp experiments we have plotted, the traces used to generate population averages, and all the data points used in statistical tests. For Figures 8-10 and Supplementary Figures 4-5, we included modeling results in the form of the plotted generated currents and spike trains, and calculated spike rates and regularity measures. We used OriginPro software to plot traces and run statistical analyses. These files can be made available upon request. Results from statistical tests can be found in the Tables reported in the paper. Relationship between files: Some data is repeated in different files if it is used in multiple figures. This is easily seen if when the unique CellID/Header for each data entry is found in multiple files. Below are the files that share the same data between them: * Fig 5.xls, Tab 1 and Supp Fig 1.xls, Tab C * Fig 5.xls, Tab 3 and Supp Fig 1.xls, Tab A * Fig 5.xls, Tab 6 and Supp Fig 1.xls, Tab B ### Data Descriptions:  *Fig 1.xls* 1. Tab 1: Fig 1B. Voltage clamp traces for Figure 1B. Column A "Time" is the time vector in milliseconds; "Ipri700BC" columns are the current responses in pA; "CmdVC700B" columns have the voltage commands in mV.  2. Tab 2: Fig 1C. Voltage clamp traces for Figure 1C. Column A "Time" is the time vector in milliseconds; column B "NaVP (sub)"is the persistent sodium current response, calculated by subtracting columns C and D, in pA; column C "Control 190207VGN2" is the current response recorded in control conditions; column D "TTX" is the current responses recorded in TTX; column E "CmdVC700B" is the voltage commands in mV.  3. Tab 3: Fig 1D. Voltage clamp traces for Figure 1D. Column A "Time" is the time vector in milliseconds; "Ipri700BC" columns B-I are the current responses in pA; "CmdVC700B" columns J - Q have the voltage commands in mV.  4. Tab 4: Fig 1E. Traces used to generate the averaged IV curve for NaVT. Columns A - C are the trace shown in Fig 1E: Column A is the averaged voltage command in mV, column B is the averaged peak current response in mV, and column C is the standard error measured. Columns D through AW are the individual examples that were averaged to generate the averaged trace (which has been downsampled); the data are listed in pairs, where the command voltage (mV) proceeds the current responses (pA), which has each CellID. 5. Tab 5: Fig 1E. Traces used to generate the averaged IV curve for NaVR. Columns H - J are the trace shown in Fig 1E: Column H is the voltage command in mV, column I is the averaged peak current response in mV, and column J is the standard error measured. Columns A through G are the individual examples that were averaged to generate the averaged trace (which has been downsampled); column A is the command voltage (mV), and columns B-G arethe current responses (pA), which are labelled with each CellID. 6. Tab 6: Fig 1E. Traces used to generate the averaged IV curve for NaVP. Columns A - C are the trace shown in Fig 1E: Column A is the voltage command in mV, column B is the averaged peak current response in mV, and column C is the standard error measured. Columns D through P are the individual examples that were averaged to generate the averaged trace (which has been downsampled); column A is the command voltage (mV), and columns B-P are the current responses (pA), which are labelled with each CellID.  7. Tab 7: Fig 1E. Data from the computational model that show the current-voltage relationship of our modeled sodium currents. NaVT: column A is command voltage (mV), column B is current response (nA). NaVR: column C is command voltage (mV), column E is current response (pA). NaVP: column E is command voltage (mV), column F is current response (pA). *Fig 2.xls* 1. Tab 1: Fig 2A. Current density (I-V) traces for activation (A-C, filled circles) and inactivation (Z-AB, open triangles) for cells with only NaVT (black). Columns D through Y, AC through AX are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the current response, normalized by cell size (nA/pF), which is labelled with each CellID.  2. Tab 2: Fig 2A: Current density (I-V) traces for activation (columns A-C) and inactivation (AB-AD) for cells with NaVT and NaVP (NaVT+P, blue).  Columns D through AA, AE through BB are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) the current response, normalized by cell size (nA/pF), which is labelled with each CellID. 3. Tab 3: Fig 2A: Current density (I-V) traces for activation and inactivation for cells with NaVT and NaVR (NaVT+R) in green. The data are listed in pairs, where the command voltage (mV) the current response, normalized by cell size (nA/pF), which is labelled with each CellID. 4. Tab 4: Fig 2A: Current density (I-V) traces for activation (A-C) and inactivation (L-N) for cells with NaVT, NaVP, and NaVR (NaVT+P+R, pink). Columns D through K, O through V are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the current response, normalized by cell size (nA/pF), which is labelled with each CellID. 5. Tab 5: Fig 2B. Conductance-Voltage (G-V) traces for activation (A-C) and inactivation (Z-AB) for cells with only NaVT (black). Columns D through Y, AC through AX are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the calculated conductance responses (nS), which is labelled with each CellID. 6. Tab 6: Fig 2B: Conductance-Voltage (G-V) traces for activation (A-C) and inactivation (AB-AD) for cells with NaVT and NaVP (NaVT+P, blue). Columns D through AA, AE through BB are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the calculated conductance responses (nS), which is labelled with each CellID. 7. Tab 7: Fig 2B: Conductance-Voltage (G-V) traces for activation (column A-C) and inactivation (P-R) for cells with NaVT and NaVR pooled with cells that had NaVT, NaVP, and NaVR (NaVT+P+R, pink). Columns D through O, S through AD are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the calculated conductance responses (nS), which is labelled with each CellID. 8. Tab 8: Fig 2C. Maximum sodium conductance density (NaV Gmax Density) values for cells with NaVT (black, NaVT+P (blue), NaVT+R (green), and NaVT+P+R (pink).  *Fig 3.xls* 1. Tab 1: Fig 3A. Voltage clamp traces as seen in Fig 3A. Column A is the time vector in milliseconds. Column B is the command voltage (bottom panel in Fig 3A). Columns C-E: NaVT current before (black trace, "Control", column C), during (red, "Residual", column D), and the subtracted (blue trace, "Blocked", column E) the application of 100 nM of 4,9-ah-TTX. 2. Tab 2: Fig 3B. Conductance-Voltage (G-V) traces for activation (column A-C) and inactivation (AD-AF) before (black) and during (red) the application of 4,9-ah-TTX, and the subtracted current (blue). Columns D through AC, AG through BF are the individual examples that were averaged to generate the averaged trace. The data are listed in pairs, where the command voltage (mV) proceeds the calculated conductance density responses (nS/pF), which is labelled with each CellID. 3. Tab 3: Fig 3C. Voltage clamp traces for Figure 3C. Column A "Time" is the time vector in milliseconds; column B "Voltage" is the voltage commands in mV; column C is the control persistent sodium current response; column D is the current responses recorded in 4,9-ah-TTX ("Residual"); column E is the "Blocked" current calculated by subtracting columns C and D, in pA. 4. Tab 3: Fig 3D. Voltage clamp traces for Figure 3D. Column A "Time" is the time vector in milliseconds; column B "Voltage" is the voltage commands in mV; column C is the control resurgent sodium current response; column D is the current responses recorded in 4,9-ah-TTX ("Residual"); column E is the "Blocked" current calculated by subtracting columns C and D (bottom panel), in pA. *Fig 4.xls* 1. Tab 1: Fig 4A. Voltage clamp traces for Figure 4A. Column A "Time" is the time vector in milliseconds; column B "Voltage" is the voltage command in mV (bottom panel); column C is the "Control" transient sodium current response; column D is the current response recorded in 100 nM ATX-II. 2. Tab 2: Fig 4B. Voltage clamp traces for Figure 4B. Column A "Time" is the time vector in milliseconds; column B "Voltage" is the voltage command in mV; column C is the "Control" persistent sodium current response; column D is the current response recorded in 100 nM ATX-II. 3. Tab 3: Fig 4C. Persistent current amplitude in control condition (column A) and after application of ATX-II (column B).  *Fig 5.xls* 1. Tab 1: Fig 5A. Current clamp traces of exemplar firing patterns. Time (column A) in ms. Sustained-A (column B), sustained-B (column C), sustained-C (column D), and transient (column E) firing patterns in mV.  2. Tab 2: Fig 5B. Maximum sodium conductance density (NaV GMax Density) values of cells with different firing patterns Sustained-A (column A), sustained-B (column B), sustained-C (column C), and transient (column D). 3. Tab 3: Fig 5C. Current clamp traces of averaged APs of each firing pattern, aligned to their peaks.  4. Tab 4: Fig 5D. Spike height (V-AP) as a function of NaV GMax Density. 5. Tab 5: Fig 5E. Afterhyperpolarization (V-AHP) values of cells with different firing patterns Sustained-A (column A), sustained-B (column B), sustained-C (column C), and transient (column D). 6. Tab 6: Fig 5F. Phase plane plots of APs from Fig 5C. The derivative of membrane voltage (dV/dt) of each firing pattern as a function of membrane voltage. 7. Tab 7: Fig 5G. Peak dV/dt as a function of NaV GMax Density. 8. Tab 8: Fig 5H. NaV GMax Density as a function of age. *Fig 6.xls* 1. Tab 1: Fig 6A. Current clamp traces as seen in Fig 6A. Column A is the time vector in milliseconds. Column B - U is the control firing pattern in order of increased current steps (black) and column V - AO are the firing pattern during the application of 100 nM of 4,9-ah-TTX. 2. Tab 2: Fig 6B. Current clamp traces as seen in Fig 6B. Column A is the time vector in milliseconds. Column B - N is the control firing pattern in order of increased current steps (black) and column O - AH are the firing pattern during the application of 100 nM of 4,9-ah-TTX. 3. Tab 3: Fig 6C. Current clamp traces of averaged APs of each firing pattern, aligned to their peaks, in control conditions (columns A - C, averaged from data in D - AC) and during 4,9-ah-TTX (columns AD - AF, averaged from data in AG - BB). 4. Tab 4: Fig 6D. Spike height in control condition (column B) and after application of 4,9-ah-TTX (column C).  5. Tab 5: Fig 6E. Afterhyperpolarization in control condition (column B) and after application of 4,9-ah-TTX (column C). 6. Tab 6: Fig 6F. Time-to-peak in control condition (column B) and after application of 4,9-ah-TTX (column C).  7. Tab 7: Fig 6G. Phase plane plots (dV/dt as a function of mV) from spikes in Fig 6C.  8. Tab 8: Fig 6H. Peak dV/dt in control condition (column B) and after application of 4,9-ah-TTX (column C).  9. Tab 9: Fig 6I and J. Resting membrane potential in sustained and transient firing VGNs in control condition (column C) and after application of 4,9-ah-TTX (column D).  10. Tab 10: Fig 6K. Spike trains evoked by injected trains of pseudo-excitatory postsynaptic currents (EPSCs, columns C and E) before (column B) and after application of 4,9-ah-TTX (column D). 11. Tab 11: Fig 6L. Spiking regularity (CV) in control condition (column B) and after application of 4,9-ah-TTX (column C).  *Fig 7.xls* 1. Tab 1: Fig 7A. Current clamp traces as seen in Fig 7A. Column A is the time vector in milliseconds. Column B - P is the control firing pattern in order of increased current steps (black) and column Q-AE are the firing pattern during the application of 100 nM of ATX-II. 2. Tab 2: Fig 7B. Current clamp traces as seen in Fig 7B. Column A is the time vector in milliseconds. Column B - P is the control firing pattern in order of increased current steps (black) and column Q-AE are the firing pattern during the application of 100 nM of ATX-II. 3. Tab 3: Fig 7C. Spike trains evoked by injected trains of pseudo-excitatory postsynaptic currents (EPSCs, columns C and E) before (column B) and after application of ATX-II (column D). 4. Tab 4: Fig 7D. Spiking regularity (CV) in control condition (column B) and after application of ATX-II (column C).  *Fig 8.xls* 1. Tab 1: Fig 8A. Firing patterns of model sustained-A, sustained-B, sustained-C, and transient VGNs under different combinations of NaV currents (NaVT only (T only), NaVT+P (T+P), NaVR (T+R), NaVT+P+R (T+P+R), or increased NaVT (T+)).  2. Tab 2: Fig 8B. Transient NaV currents of model sustained-A, sustained-B, sustained-C, and transient VGNs under different combinations of NaV currents (NaVT only (T only), NaVT+P (T+P), NaVR (T+R), NaVT+P+R (T+P+R), or increased NaVT (T+)). 3. Tab 3: Fig 8C. Resurgent NaV currents of model sustained-A, sustained-B, sustained-C, and transient VGNs under different combinations of NaV currents ( NaVR (T+R) or NaVT+P+R (T+P+R)). 4. Tab 4: Fig 8D. Persistent NaV current of model sustained-A, sustained-B, sustained-C, and transient VGNs under different combinations of NaV currents (NaVT+P (T+P) or NaVT+P+R (T+P+R). 5. Tab 5: Fig 8E and F. First action potentials from firing patterns and their phase plane plots of model sustained-A, sustained-B, sustained-C, and transient VGNs under different combinations of NaV currents (NaVT only (T only), NaVT+P (T+P), NaVR (T+R), NaVT+P+R (T+P+R), or increased NaVT (T+)).  *Fig 9.xls* 1. Tab 1: Fig 9A and B. Exemplar spike trains of model sustained-A (Fig 9A) and transient (Fig 9B) VGN evoked by trains of pseudo-EPSCs (column B), under different NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 2. Tab 2: Fig 9C. Spike rate as a function of NaV conductance (gNaVT) in model sustained-A, in different NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 3. Tab 3: Fig 9E. Spike regularity (CV) as a function of NaV conductance (gNaVT) in model sustained-A, in different NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 4. Tab 4: Fig 9G. Spike regularity at a fixed spike rate (20 spikes/s) (CV-20sp/s) as a function of NaV conductance (gNaVT,) in model sustained-A, indifferent NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 5. Tab 5: Fig 9D. Spike rate as a function of NaV conductance (gNaVT) in model transient, in different NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 6. Tab 6: Fig 9F. Spike regularity (CV) as a function of NaV conductance (gNaVT) in model transient, in different NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). 7. Tab 7: Fig 9H. Spike regularity at a fixed spike rate (20 spikes/s) (CV-20sp/s) as a function of NaV conductance (gNaVT) in model transient, indifferent NaV current combinations (NaVT, NaVT+P, NaVT+R, NaVT+P+R). *Supp Fig 1.xls (note Supp Fig 1-C is same data as Fig 5A, C, F)* 1. Tab 1: Supp Fig1D and E. First action potentials from firing patterns and their phase plane plots of model sustained-A, sustained-B, sustained-C, and transient VGNs. 2. Tab 2 Supp Fig 1 F:Exemplar spike trains of model model sustained-A, sustained-B, sustained-C, and transient VGNs evoked by current steps. *Supp Fig 2.xls* 1. Tab 1: Supp Fig 2: Traces from Fig 2, showing the different shapes of EPSCs used in this study (sV, column B) and in Hight and Kalluri, 2016 (s1, s2, s3) . 2. Tab 2: The raw data of sV, included the averaged EPSC and the model fit.  *Supp Fig 3.xls* 1. Tab 1: Supp Fig 3. Distribution of firing patterns as a function of age (days) of cell.  *Supp Fig 4.xls* 1. Tab 1: Supp Fig 4A: Modeled current clamp traces . Column A is the time vector in milliseconds. Column B, D, F are the control Sustained-A firing pattern in order of increased current steps (black) and column C, E, G are the firing pattern during simulated 70% "block" (reduction) of NaVT current and 90% "block" (reduction) in NaVP and NaVR. 2. Tab 2: Supp Fig 4B: Modeled current clamp traces . Column A is the time vector in milliseconds. Column B, D, F are the control transient firing pattern in order of increased current steps (black) and column C, E, G are the firing pattern during simulated 70% "block" (reduction) of NaVT current and 90% "block" (reduction) in NaVP and NaVR. 3. Tab 3: Fig 4C. Simulated changes in membrane potential during "blocks" (reduction of) difference NaV current combinations in a sustained-A model VGN.  *Supp Fig 5.xls* 1. Tab 1: Fig 9A and B. Exemplar spike trains of model sustained-A (Fig 9A) and transient (Fig 9B) VGN evoked by trains of pseudo-EPSCs (column B), under increased NaVP current conditions (0, 3, 5, 8, 10%). 2. Tab 2: Fig 9C and D. Spike rate as a function of NaV conductance (gNaVT) in model sustained-A and transient, in increased NaVP current conditions (0, 3, 5, 8, 10%). 3. Tab 3: Fig 9E and F. Spike regularity (CV) as a function of NaV conductance (gNaVT) in model sustained-A and transient, in increased NaVP current conditions (0, 3, 5, 8, 10%). **List of abbreviations used in files** Currents: NaVT: transient voltage-gated sodium current, also used to denote a case where there is only transient sodium current NaVP: persistent voltage-gated sodium current NaVR: resurgent voltage-gated sodium current NaVT+P: data from VGN that expressed both transient and persistent NaV currents NaVT+R: data from VGN that expressed both transient and resurgent NaV currents NaVT+P+R: data from VGN that expressed all NaV current modes IV: Current as a function of voltage GV: Conductance as a function of voltage Pharmacology: TTX: tetrodotoxin (global NaV channel blocker) 4,9-ah-TTX: 4,9-anhydrotetrodotoxin (NaV1.6 channel specific blocker) ATX-II: Anemonia viridis toxin 2 (NaV channel agonist) Spiking: CV: coefficient of variance ## Code/Software Associated code for statistical analysis (effect size, Hedges' g), EPSC fitting, voltage clamp model of multiple voltage-gated sodium currents, and our extended Hodgkin-Huxley model for vestibular ganglion neuron spiking can be found in the following repository: [https://github.com/eatocklab/NaV-currents-in-VGN-spiking.git](https://github.com/eatocklab/NaV-currents-in-VGN-spiking.git)