TTX-R Na+ current effect on cell response (Herzog et al 2001)

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"Small dorsal root ganglion (DRG) neurons, which include nociceptors, express multiple voltage-gated sodium currents. In addition to a classical fast inactivating tetrodotoxin-sensitive (TTX-S) sodium current, many of these cells express a TTX-resistant (TTX-R) sodium current that activates near -70 mV and is persistent at negative potentials. To investigate the possible contributions of this TTX-R persistent (TTX-RP) current to neuronal excitability, we carried out computer simulations using the Neuron program with TTX-S and -RP currents, fit by the Hodgkin-Huxley model, that closely matched the currents recorded from small DRG neurons. ..." See paper for more and details.
1 . Herzog RI, Cummins TR, Waxman SG (2001) Persistent TTX-resistant Na+ current affects resting potential and response to depolarization in simulated spinal sensory neurons. J Neurophysiol 86:1351-64 [PubMed]
Model Information (Click on a link to find other models with that property)
Model Type: Neuron or other electrically excitable cell;
Brain Region(s)/Organism:
Cell Type(s): Dorsal Root Ganglion (DRG) cell;
Channel(s): I Na,p; I Na,t; I K;
Gap Junctions:
Gene(s): Nav1.1 SCN1A; Nav1.6 SCN8A; Nav1.7 SCN9A; Nav1.8 SCN10A; Nav1.9 SCN11A SCN12A;
Simulation Environment: NEURON;
Model Concept(s): Ion Channel Kinetics; Nociception;
Implementer(s): Morse, Tom [Tom.Morse at];
Search NeuronDB for information about:  I Na,p; I Na,t; I K;
// create_cell.hoc
// creates cell from Herzog, Cummins, Waxman 2001
// implemented by Tom Morse version 2/25/07

create soma
access soma

// set the cell area:
// let PI*diam*L=3000 (um)^2 then if diam is defined to be equal to L
diam = sqrt(3000/PI)
L = diam

// cm is assigned below so that 3000 (um^2) area leads to a
// capacitance of 24.3 pF:
cm = 0.81 // uF/cm2

// the cytosol resistance is given in the paper as 200 Ohm/cm
// I think they mean Ohm*cm
Ra = 200 // Ohm*cm

// insert channels into membrane

insert nattxs
insert nav1p9
insert kdr
// the passive channel parameters are set here
insert pas

// the stated input resistance of the model cell is 300 MOhms
// which corresponds to a total conductance of
// 1/(300 MOhms) = 1/300e-6 = 3.3e-9 S
// which in turn implies a specific conductance
// 3.3e-9 S/(3000 (um^2) which in S/cm2 is
//g_pas = 0.00011 // note that the paper also mentions
g_pas = 0.00014		// 0.00014 S/cms which corresponds to 238 MOhms
// using either leak conductances has similar results
e_pas = -54.3 // slightly higher leak potential than usual

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