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IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 5:27 am
by shd
Hi,
I built a very simple model:
Code: Select all
load_file("nrngui.hoc")
create soma
access soma
soma {
nseg = 1
diam = 18
L = 18
Ra = 123.0
insert hh
gnabar_hh = 132
}
// create an electrode in the soma
objectvar stim
soma stim = new IClamp(0.5)
stim.del = 350
stim.dur = 100
stim.amp = 1
tstop = 500
The problem is that when I change gnabar_hh to a high value, there's no delay in the IClamp.
I noticed that the maximum value, which the delay works with, changes when I change the soma diameter and length.
In adittion, changing the potassium conductance doesn't make any difference.
What may cause the problem?
Thanks in advance...
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 10:44 am
by ted
shd wrote:The problem is that when I change gnabar_hh to a high value, there's no delay in the IClamp.
. . .
In adittion, changing the potassium conductance doesn't make any difference.
These are inferences that you have drawn. What is the evidence that leads you to these inferences?
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 12:31 pm
by shd
I ment that the potassium channel conductace (gkbar) doesn't make any difference. (Just to be clear, it does change the voltage but it doesn't cause the delay not to work).
I know it, because I tried to change the value of gkbar on a broad range of values and the delay was still working.
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 1:32 pm
by ted
What is your evidence that "the delay doesn't work"?
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 1:56 pm
by shd
The graph, voltage vs. time. I got an action potenthial immediately (0<t<5), when the stimulation need to be in time t=350. or maybe I misunderstood the whole idea?
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 3:23 pm
by ted
shd wrote:The graph, voltage vs. time. I got an action potenthial immediately
And that is the evidence that the current pulse delivered by the IClamp begins at t=0? You changed a property of the model cell, observed an effect on membrane potential in the model cell, and this means that something in the _IClamp_ has changed? Where is the evidence that the current pulse delivered by the IClamp starts at t = 0?
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 4:30 pm
by shd
Thank you.
Re: IClamp, Delay and HH channel conductance
Posted: Sun Dec 12, 2010 4:40 pm
by ted
Plot or print the current delivered by the IClamp as a function of time and see if changing gnabar_hh has any effect on when the current pulse starts. If you're not sure how to create such a plot, see
Q: How do I plot something other than membrane potential?
in NEURON's FAQ list
http://www.neuron.yale.edu/neuron/faq/general-questions