NaV1.8 | sodium voltage-gated channel alpha subunit 10

Family:
Sodium channels

Subgroups:
Na_V1.1-1.9

Topology:
Alpha subunits consist of four homologous domains (I-IV) with six transmembrane alpha helices (S1–S6) and a pore-forming loop. One a subunit may associate with 1 or 2 b subunits to make up the channel.

NaV1.8: Background Information

Na_V1.8 is expressed specifically in the dorsal root ganglion (DRG), in unmyelinated, small-diameter sensory neurons called C-fibres, and is involved in nociception. C-fibres can be activated by noxious thermal or mechanical stimuli and thus can carry pain messages. The specific location of Na_V1.8 in sensory neurons of the DRG may make it a key therapeutic target for the development of new analgesics and the treatment of chronic pain. Na_V1.8 is a TTX-resistant sodium channel.

Gene:
SCN10A

Human Protein:
UniProt Q9Y5Y9

Tissue:
Brain (small diameter DRG neurons)

Function/ Application:
Excitability of neurons, nociceptive transmission

Pathology:
Neuropathic pain, Multiple Sclerosis

Accessory subunits:
b1, b2, b3

Interaction:
p11, PDZD2 and syntrophin-associated serine/threonine kinase (SASTK), Contactin, CAP-1A

Modulator:
Tetrodotoxin, lidocaine, benzocaine, A-887826, A-803467

Assays:
Patch Clamp: whole cell, room temperature, State- and use-dependence

Particularities:
Na_V channel analysis requires GigaOhm seals and a stable and low access resistance

Recommended Reviews:
International Union of Pharmacology. XLVII. Nomenclature and Structure-Function Relationships of Voltage-Gated Sodium Channels. Pharmacol Rev 57: 397–409, Catterall, et al. 2005

Data and Applications

NaV1.8 - State Dependent Inhibition

SyncroPatch 384PE data and applications:
Cells were kindly provided by Charles River.

The state dependent inhibition of Tetracaine on Na_V1.8 currents were investigated. Measured on the SyncroPatch 384PE the perforated cell patch methodology (Escin) and multi-hole chips were used and compared to single-whole chips. Using a state dependant pulse protocol, the IC₅₀ value determined from the first pulse (C1) was calculated as 54.3 µM (Hill coefficient = 1.50), and from the second pulse (C2) as 1.27 µM (Hill coefficient = 0.62).

NaV1.8 - Voltage Dependent Block by Tetracaine

Patchliner data and applications:
Cells were kindly provided by Millipore.

Recordings were made on the Pachliner. The potency of tetracaine was affected by holding potential, becoming less potent with a more negative holding potential. Average concentration response curve for tetracaine, IC₅₀ = 35 ± 8 μM (n = 3) for Vhold - 90 mV and 74 ± 15 μM (n = 4) for Vhold - 120 mV.

NaV1.8 - Tetracaine Pharmacology

Patchliner data and applications:
Cells were kindly provided by Millipore.

A Raw traces from an exemplar cell recorded on the Patchliner showing inhibition of current by increasing concentrations of tetracaine. Shown are current responses to a single step protocol to 20 mV for 25 ms from a holding potential of -90 mV. Current amplitude was completely recovered upon washout of tetracaine (red trace).
B Timeplot of the experiment.

NaV1.8 - Current-Voltage Relationship

Patchliner data and applications:
Cells were kindly provided by Millipore.

A Raw traces from an exemplar cell recorded on the Patchliner. Shown are current responses to increasing voltage steps from -80 to +60 mV.
B Average current-voltage plot, Vhalf of activation was -9 mV (n = 19).
C Average inactivation plot, Vhalf of inactivation was -24 mV (n = 4). Na_V1.8 currents started to activate at about -40 mV, peak response was elicited at around 20 mV.

NaV1.8 - Block by Tetracaine

SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.

A Raw traces from an exemplar cell recorded on the SyncroPatch 96 showing inhibition of current by increasing concentrations of tetracaine. Shown are current responses to a single step protocol to 20 mV for 25 ms from a holding potential of -120 mV.
B Average concentration response curve for tetracaine, IC50 = 71 ± 5 μM (n = 40).

NaV1.8 - Block by Lidocaine

SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.

A Raw traces from an exemplar cell recorded on the SyncroPatch 96 showing inhibition of current by increasing concentrations of lidocaine. Shown are current responses to a single step protocol to 20 mV for 25 ms from a holding potential of -120 mV.
B Average concentration response curve for lidocaine, IC50 = 178 ± 11 μM (n = 35).

NaV1.8 - I/V Characteristics

SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:

The ND7-23 cells were kindly provided by Millipore.

A Raw traces from an exemplar cell recorded on the SyncroPatch 96. Shown are current responses to increasing voltage steps from -60 to +60 mV.
B Average current-voltage plot, Vhalf of activation was 12 mV (n = 32).
C Average inactivation plot, Vhalf of inactivation was -27 mV (n = 32). Nav1.8 currents started to activate at about -30 mV, peak response was elicited between 20 and 30 mV and Vhalf of activation was 12 mV. The Vhalf of inactivation was -27 mV in good agreement with the literature.

NaV1.8 - Success Rate & Access Resistance

SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
The cells were kindly supplied by Millipore.

A Success rate (seal resistance) of ND7-23 cells on the SyncroPatch 96. Shown is a bar graph of seal resistances on the SyncroPatch 96 at the start (blue) and end (grey) of the experiment.
B Bar graph of cell capacitance (Cslow) of ND7-23 cells. Mean Cslow = 22.6 ± 0.8 pF (n = 88 ).
C Bar graph of series resistance (Rs) values for ND7-23 cells on the SyncroPatch 96. Mean Rs = 7.1 ± 0.4 MΩ (n = 88).

NaV1.8 - Automated Analysis

SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by EMD Millipore.

With the SyncroPatch Analysis Tool - DataControl96, IC₅₀ plots are easily generated, displayed, averaged, evaluated, and modified.
Here, Lidocaine concentration response curves (CRC) of rNa_V1.8 expressing ND7-23 cells are shown.