This is the readme.txt for the model associated with the paper:
Brown AM. A modeling study predicts the presence of voltage gated
Ca(2+) channels on myelinated central axons.
Comput Meth Prog Biomed 2003;71:25-31.


The objective of this current study was to investigate whether voltage
gated Ca(2+) channels are present on axons of the adult rat optic
nerve (RON). Simulations of axonal excitability using a Hodgkin-Huxley
based one-compartment model incorporating I(Na), I(K) and leak
currents were used to predict conditions under which the potential
contribution of a Ca(2+) current to an evoked action potential could
be measured. Under control conditions the inclusion of a high
threshold Ca(2+) current (I(Ca)) in the model had a negligible effect
on the action potential. Reducing I(K), by decreasing the value of
g(K), elongated the repolarizing phase of the action potential,
increasing its duration. Subsequent incorporation of I(Ca) in the
model revealed a significant I(Ca) contribution to the repolarizing
phase of the action potential. The simulation thus suggests that
Ca(2+) channels may be present on RON axons, but that pharmacological
intervention is required to unmask their presence.  Experiments based
on the simulations revealed that there was no significant contribution
of I(Ca) to the control action potential. However, as predicted by the
simulation, reducing the repolarizing effect of I(K) by adding the
K(+) channel blocker 4-AP revealed a Ca(2+) component on the
repolarizing phase of the action potential that was blocked by the
Ca(2+) channel inhibitor nifedipine.


To run the model:
XPP: start with the command
xppaut AP-sim-Ca.ode
Then click on Initialconds -> (G)o

This simulation will make graphs similar to Figure 1 in the paper by


Changes in conductance of potassium and/or calcium currents can also
be implemented.

Bard Ermentrout's website: describes how
to get and use XPP.

This model file was submited by:

Dr. Sheng-Nan Wu
Department of Pharmaololgy & Toxicology
Virginia Commonwealth Univesity School of Medicine
Richmond, Virginia USA
wshengnan at