current between two compartments

[thats_karlo]

Hi,

Suppose we have a 2-compartment model with different currents in these two compartments. we inject current and measure membrane potential in the first one.

consider this case: we have injected a constant depolarized current, for a specific duration, in the middle of fist compartment

how can we determine,
1- the value of (total/individual) current that reach to second one and depolarize it?

(after some times the feedback current)

2- the value of (total/individual) current coming from second one to the first compartment?


Thanks in advance,

Karlo

[ted]

http://www.neuron.yale.edu/neuron/stati ... ry.html#ri

[thats_karlo]

Dear Ted,

Thanks for very fast reply!!

[ted]

When you're not sure about the meaning of something in the Programmer's Reference,
do an experiment that removes the ambiguity. In this case, make a toy model. Calculate
the values by hand. Compare with what you get from ri().

[thats_karlo]

Dear Ted,

please tell me am i right or no?

I have two compartments model, different currents, with following topology

________
| dend[0] |__________
| dend[0] | dend[1] |
|_______|--------------


and forall nseg=3


dose

Code: Select all

 dend[1] {  ( v(0.16)- v(0) )/ri(0.16) }

means axial current between to compartments?

[ted]

I have two compartments model, different currents, with following topology
________
| dend[0] |__________
| dend[0] | dend[1] |
|_______|--------------

and forall nseg=3

Then it isn't a two compartment model, is it?

Code: Select all

 dend[1] {  ( v(0.16)-.v(0) )/ri(0.16) }

means axial current between to compartments?

Absolutely correct. In that expression, ri(0.16) is the axial resistance between the first
internal node of dend[1] and the node at the 0 end of dend[1]. v(0.16) and v(0) are
the membrane potentials at those nodes. Therefore v(0.16) - v(0) is the voltage gradient
across the axial resistance, and the ratio v(0.16) - v(0) / ri(0.16) is the axial current that
enters the 0 end of dend[1]. This is equal to the axial current that leaves the 1 end of
dend[0].

But what are the units of this current?

[thats_karlo]

Thanks Ted,


1- probably, i should say, we have two sections, with nseg=3, which means 6-compartment,right?

2-I think the unite for axial current is nA, right?

Yours,

Karlo

[ted]

True and true. Good work, Karlo.

[thats_karlo]

Hello Ted,

Could you please tell me the following formula is a right method to calculate total current that depolarized cell,(in the soma to reach threshold to firing); I=I1+I2+I3, where

I1=(Ionic current+leak current)*area(0.5)/100 // (like Na+/K+, Ca2+,...) in [nA]
I2=(v(0.5)-v(1))/ri(1) // axial current toward to soma
I3=Iinj // injected current


Karlo

[ted]

That would work, as long as the default section has nseg = 1. If nseg is not 1, you need
to do
totalarea = 0
for (x, 0) totalarea += area(x)
and then change the equation for I1 to
I1=(Ionic current+leak current)*totalarea/100 // (like Na+/K+, Ca2+,...) in [nA]