This is a readme for a model associated with 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 NEURON files were created by Tom Morse. Usage: Simply auto-launching from ModelDB will cause a panel of buttons to pop up where the Figure 2 button will create a picture similar to fig 2 in the paper: Similarly for the figure 4 button: Alternatively you can: 1) download and extract the files. 2) Compile the mod files as usual on your platform (run mknrndll under windows, execute nrnivmodl in the extracted directory under linux, or drag and drop the extracted folder onto the mknrndll icon under mac os x). 3) Then start mosinit.hoc (double click on mosinit.hoc in windows, type "nrngui mosinit.hoc" in linux, or drag and drop the mosinit.hoc file onto the nrngui icon in mac os x). The above described figure buttons are created. April 28th, 2009 Bug fixes in KDR supplied by Tom Andersson. The reversal potential and the ninf in KDR were corrected to those in the paper. Also Andersson suggested using the leak conductance value given in the paper (the one corresponding to 300 MOhm can also be used with a trivial difference in results). The paper value was implemented.