This is the readme for a matlab version of a model from the paper

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

Abstract:

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. In contrast to fast TTX-S
current, which was well fit using a m(3)h model, the persistent TTX-R
current was not well fit by an m(3)h model and was better fit using an
mh model. The persistent TTX-R current had a strong influence on
resting potential, shifting it from -70 to -49.1 mV. Inclusion of an
ultra-slow inactivation gate in the persistent current model reduced
the potential shift only slightly, to -56.6 mV. The persistent TTX-R
current also enhanced the response to depolarizing inputs that were
subthreshold for spike electrogenesis. In addition, the presence of
persistent TTX-R current predisposed the cell to anode break
excitation. These results suggest that, while the persistent TTX-R
current is not a major contributor to the rapid depolarizing phase of
the action potential, it contributes to setting the electrogenic
properties of small DRG neurons by modulating their resting potentials
and response to subthreshold stimuli.

Note: These MATLAB functions were created by Tom Andersson.

Usage:
Download and expand this archive.  At the matlab prompt first cd
to the newly created HerzogEtAl2001 folder then type

DRGmodel

After a minute or so the simulation finishes.  You can view the
results for example with commands like plot(Vm) which yields:

FIGURE 1: Na WITHOUT TTX-R


FIGURE 2. Na WITH TTX-R and ultra-slow gate


Note that DRGmodel_all.txt contains all the matlab code in one file for
easier examination.