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<html><pre>
This is the readme.txt for the model associated with the paper

Adrian RH, Chandler WK and Hodgkin AL. Voltage clamp experiments in 
striated muscle fibres. J Physiol 1970;208:607-644

Abstract:
1. Membrane currents during step depolarizations were determined by 
a method in which three electrodes were inserted near the end of a 
fibre in the frog's sartorius muscle. The theoretical basis and 
limitations of the method are discussed.
2. Measurements of the membrane capacity (CM) and resting resistance 
(RM) derived from the current during a step change in membrane 
potential are consistent with values found by other methods.
3. In fibres made mechanically inactive with hypertonic solutions 
(Ringer solution plus 350 mM sucrose) step depolarizations produced 
ionic currents which resembled those of nerve in showing (a) an early 
transient inward current, abolished by tetrodotoxin, which reversed 
when the depolarization was carried beyond an internal potential of 
about +20 mV, (b) a delayed outward current, with a linear instantaneous 
current-voltage relation, and a mean equilibrium potential with a normal 
potassium concentration (2.5 mM) of -85 mV.
4. The reversal potential for the early current appears to be consistent
with the sodium equilibrium potential expected in hypertonic solutions.
5. The variation of the equilibrium potential for the delayed current 
(V'K) with external potassium concentration suggests that the channel 
for delayed current has a ratio of potassium to sodium permeability of 
30:1; this is less than the resting membrane where the ratio appears 
to be 100:1. V'K corresponds well with the membrane potential at the 
beginning of the negative after-potential observed under similar conditions.
6. The variation of V'K with the amount of current which has passed 
through the delayed channel suggests that potassium ions accumulate in a 
space of between 1/3 and 1/6 of the fibre volume. If potassium accumulates in 
the transverse tubular system (T system) much greater variation in V'K 
would be expected.
7. The delayed current is not maintained but is inactivated like the early 
current. The inactivation is approximately exponential with a time constant 
of 0.5 to 1 sec at 20¢X C. The steady-state inactivation of the potassium 
current is similar to that for the sodium current, but its voltage 
dependence is less steep and the potential for half inactivation is 20 mV 
rate more positive.
8. Reconstructions of ionic currents were made in terms of the parameters
(m, n, h) of the Hodgkin-Huxley model for the squid axon, using constants 
which showed a similar dependence on voltage.
9. Propagated action potentials and conduction velocities were computed for 
various conditions on the assumption that the T system behaves as if it were 
a series resistance and capacity in parallel with surface capacity and the 
channels for sodium, potassium and leak current. There was reasonable 
agreement with observed values, the main difference being that the 
calculated velocities and rates of rise were somewhat less than those 
observed experimentally.

----------------

To run the models:
XPP: start with the command
xpp ode\muscleAP.ode
This simulation will make graphs similar to figure 23B in the paper:

<img src="AP.JPG" alt="AP.JPG">

Bard Ermentrout's website <a href="http://www.pitt.edu/~phase/">http://www.pitt.edu/~phase/</a>
describes how to get and use xpp.

These model files were submitted by:

Dr. Sheng-Nan Wu
National Cheng Kung University Medical Center
Tainan 70101, Taiwan
snwu@mail.ncku.edu.tw
</pre></html>

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Action potential of striated muscle fiber (Adrian et al 1970)

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