Total current during action potential

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Lofflery

Total current during action potential

Post by Lofflery » Wed Nov 04, 2009 11:08 am

Is it possible to plot the total net current during action potential?
I could plot current of Na or K but I need the whole current.

Bests
Loffler Yourganov

ted
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Re: Total current during action potential

Post by ted » Wed Nov 04, 2009 6:28 pm

Lofflery wrote:Is it possible to plot the total net current during action potential?
I could plot current of Na or K but I need the whole current.
Yes, but you must define what you mean by "total net current." Do you mean "total membrane current" or sum of membrane ionic currents?

If you mean "total membrane current" (sum of ionic and capacitive current) the easiest thing to do is to insert the extracellular mechanism. Then you can plot i_membrane. This is easy, but there is one caveat: i_membrane does not include contributions from ELECTRODE_CURRENT point processes. Examples of such point processes include IClamps, SEClamps, and VClamps. If in doubt about any point process, examine the NMODL source code

If you mean "sum of membrane ionic currents" you have to add them up yourself. If you are using
NEURON Main Menu / Graph / Current axis
enter the appropriate expression into the "Plot what" tool's edit field. For example, in a section that contains only the hh mechanism, you would type

Code: Select all

ina+ik+il_hh
If you are writing hoc code to add a plot to a Graph whose objref is g, you would use the following statement:

Code: Select all

g.addexpr("ina+ik+il_hh")

mschoi2

Re: Total current during action potential

Post by mschoi2 » Thu Apr 13, 2017 1:21 pm

Hi Dr. Carnevale,

Thank you so much for your detailed explanation. This helps me a lot, although this post has been inactive for 8 years.
I am trying to achieve the same thing, monitoring the total membrane ionic currents, but with nonspecific current and SEClamp.

I am little bit puzzled because I am not sure if there is any electrode current with SEClamp. Also I am sure how it will affect the nonspecific current.
What would be the best way to keep track of total membrane ionic current in my case?
Thank you again.

Min.

ted
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Re: Total current during action potential

Post by ted » Thu Apr 13, 2017 2:47 pm

mschoi2 wrote:I am little bit puzzled because I am not sure if there is any electrode current with SEClamp.
The current injected by an SEClamp is an electrode current.
Also I am sure how it will affect the nonspecific current.
Why not do the experiment and find out? And, of course, let me know what you discover. Suggest you do this with a simple model--just one or two compartments, max.

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