IClamp, Delay and HH channel conductance

The basics of how to develop, test, and use models.
Post Reply
shd

IClamp, Delay and HH channel conductance

Post 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...
ted
Site Admin
Posts: 5810
Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
Contact:

Re: IClamp, Delay and HH channel conductance

Post 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?
shd

Re: IClamp, Delay and HH channel conductance

Post 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.
ted
Site Admin
Posts: 5810
Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
Contact:

Re: IClamp, Delay and HH channel conductance

Post by ted »

What is your evidence that "the delay doesn't work"?
shd

Re: IClamp, Delay and HH channel conductance

Post 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?
ted
Site Admin
Posts: 5810
Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
Contact:

Re: IClamp, Delay and HH channel conductance

Post 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?
shd

Re: IClamp, Delay and HH channel conductance

Post by shd »

Thank you.
ted
Site Admin
Posts: 5810
Joined: Wed May 18, 2005 4:50 pm
Location: Yale University School of Medicine
Contact:

Re: IClamp, Delay and HH channel conductance

Post 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
Post Reply