In order to understand how the ionic current works I have built the following files:

mechanism.hoc

mechanism1.mod

mechanism2.mod

Mechanism1 and mechanism2 are basically the same mechanism, the only difference is that:

in 1 I am adding to the ionic current while in 2 I am subtracting from the ionic current.

Below are also the results of running mechanism1.hoc and mechanism2.hoc

My question is why is the soma.v roughly the same for both mechanisms?

My understanding is that the "density" ionic current (mA/cm2) is added to the voltage

(after multiplying it with area() section and scale cm2->um2) in order to get the total

membrane current.

Any help would be greatly appreciated.

mechanism1 result

Code: Select all

```
area=886.68311 um2
---------------------------------------
soma { nseg=1 L=16.8 Ra=210
/*location 0 attached to cell 0*/
/* First segment only */
insert morphology { diam=16.8}
insert capacitance { cm=1}
insert object {}
insert tca_ion { etca=130}
}
BREAKPOINT t=0 v=-64.999 itca=0 etca=130
.......................
BREAKPOINT t=19.95 v=-24.4036 itca=403 etca=130
```

Code: Select all

```
......................
BREAKPOINT t=0 v=-64.999 itca=0 etca=130
......................
BREAKPOINT t=19.95 v=-24.4044 itca=-403 etca=130
```

Code: Select all

```
TITLE object
UNITS {
(mA) = (milliamp)
(mV) = (millivolt)
FARADAY = 96520 (coul)
R = 8.3134 (joule/degC)
KTOMV = .0853 (mV/degC)
}
PARAMETER {
v (mV)
celsius = 6.3 (degC)
}
NEURON {
SUFFIX object
USEION tca READ etca WRITE itca VALENCE 2
RANGE itca, etca, I0
}
STATE {
I0
}
ASSIGNED {
itca (mA/cm2)
etca (mV)
}
INITIAL {
I0 = 0
itca = 0
}
BREAKPOINT {
printf("BREAKPOINT t=%g v=%g itca=%g etca=%g \n", t, v, itca, etca)
SOLVE states METHOD derivimplicit
itca = itca + 1
}
DERIVATIVE states {
I0' = I0
}
```