ionic current recording

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xiaosage
Posts: 16
Joined: Sat May 11, 2013 10:01 am

ionic current recording

Post by xiaosage »

I want to record all the individual ionic currents in soma in a NEURON model when a stimulus is performed. However, there are two types of potassium channels named "kdr" and "kap" inserted in the soma. Through the main menu "Graph-Current axis-Plot what" I only found "ik" that might be related with these two potassium currents. In the NMODL file, both of them use the same expression "ik" and declare the same USEION as "k".

My question is, is this "ik" the sum of the two types of potassium currents or just one of them? Many thanks.
ted
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Re: ionic current recording

Post by ted »

If the "Plot what?" tool constructs different hoc names for the two iks, they are different variables. Example: suppose one mechanism's NEURON block contains the statement
SUFFIX kdr
and the other one has
SUFFIX kap
and the "Plot what?" tool constructs
ik_kdr
for the first mechanism and
ik_kap
for the second, these will indeed be different variables.

Purely as a matter of esthetics, I prefer to avoid variable names that contain unnecessary duplications, and would write NMODL code that looks like this example:

Code: Select all

NEURON {
  SUFFIX kap
  USEION k READ ek WRITE ik
  RANGE gbar, i
  . . .
}
  . . .
BREAKPOINT {
  i = gbar*n^4*(v-ek)
  ik = i
}
Then I can specify gbar_kap and plot i_kap, rather than having to mess with ugly hiccups like gkbar_kap and ik_kap.
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